*CHART2: Default Colours*
"Color used well can enhance and clarify a presentation. Color used
poorly will obscure, muddle and confuse.*
-- Maureen Stone
Unfortunately, people have difficulty learning this simple fact. I just
voted for the new default pallet to be used in Chart2, yet I was NOT
very impressed by the various pallets. The last colour scheme (number
12, blue - yellow) is probably the better one, but even this one lacks
professionalism.
*What is the problem*?
As the first quote from Maureen Stone says, *too many colors* will
obscure and confuse. Therefore I will try to expand this concept further
and add some *real-life examples* from professional presentations.
A few remarks are needed before expanding this issue:
1.) EXAMPLES
============
I will add some examples as jpg-images to better show the reasoning for
the colours.
I attach some *professional charts* taken from the WHO 2005 and 2006
reports. The full reports (some 5 - 7 MB) can be downloaded from
http://www.who.int/entity/whr/2005/whr2005_en.pdf and
http://www.who.int/whr/2006/whr06_en.pdf (while for older reports see
http://www.who.int/whr/previous/en/index.html). Please take a look at
these charts, they look really good.
2.) BLACK-WHITE
===============
Sometimes, charts get printed on *black-white printers*, or colour
presentations are copied on a *black-white photocopying machine* (quite
often). Many colour-schemes fail poorly in this instance due to poor
contrast/luminosity difference between 2 neighboring fields.
3.) PREVIOUSLY e-MAILED
=======================
2.) I e-mailed a similar post to the chart mailing list. However,
presumably because I appended some jpg-images, the post never showed up.
2'.) I sent a similar e-mail (with jpg-attachements) directly to people
working for Sun (e.g. to Ingrid Halama), but got NO response either, so
it was presumably deleted as well.
2''.) this is my third attempt and I will post it as a comment to issue
7019 (http://www.openoffice.org/issues/show_bug.cgi?id=7019). I will
attach the beforementioned jpg-images to that issue, too. This is a
greatly expanded review.
3.) TOC
=======
This document will be organised as follows:
a. INTRODUCTION
b. BAR CHARTS
b'. 2-3 Colours
b''. MONOCHROME MODEL
c. PIE CHARTS and other Chart Types
d. DEFAULT EXAMPLES
e. CONCLUSIONS
a. INTRODUCTION
===============
Colours used in a chart should clarify the chart and *NOT confuse the
viewer*. Unfortunately, this is difficult when choosing many colours as
they 1.) tend to *distract* the viewer from the relevant information and
2.) *obscure* some of the colours used.
This is the reason why professional presentations *never* use more than
5 different colour groups (hue-groups). Actually, IF more groups seem to
be needed, there are 2 ways to resolve this issue:
- either the user does NOT recognise the *essential parts* in the chart
(to *highlight* only the *essential information*), or
- (IF – rarely – the previous statement does NOT apply) use basically a
*single hue-group*
This will be further expanded for *BAR-Charts* and separately for the
*OTHER-Chart types*.
b. BAR CHARTS
=============
Bar charts are likely to contain many groups of data. A common mistake
is to draw every BAR in a *different colour*. This is both unnecessary
and obstructs the meaning of the bar chart.
A good colour-scheme will have to distinguish between:
B1. are there only 2 groups of data: then use of 2 oppsoing colours
(significantly different hues) is OK. Also, make the luminosity
different, so that black-white printing looks good, too.
B2. are there 3-5 groups of data: selecting 3 to 5 different colours is
feasible, BUT alternatives using only 1-2 colours are equally effective.
B3. more than 5 bars: *NEVER* use more than 5 colour-groups!!!
To quote Maureen Stone again:
"In most design situations, the best results are achieved by limiting
hue to a palette of two or three colors, and using hue and chroma
variations within these hues to create distinguishably different colors.
Such a palette is both aesthetically pleasing and functional. It
minimizes an over-dependence on hue variation (which can cause visual
clutter), and replaces it with careful control of value and chroma.
Figure 8 shows several such palettes, and their location on the hue wheel."
-- Maureen Stone
There are some solutions to this problem:
i.) do we need to *highlight SOMETHING*?
NO => just use the same colour for every bar (*MONOCHROME*)
ii.) IF we need to highlight 1 or 2 groups of data, apply a different
colour only to those 1-2 groups (maximum colours used = 3). IF you need
to highlight more than 3 groups, you are doing something wrong.
[in the rare situation, where a bar graph is drawn for a group of 4 or
more items repeated several times, use either monochrome, or see later
for pie-charts, BUT strong consideration should be given NOT to compare
2 or more groups of MORE THAN 4 items each]
C. PIE CHARTS (& other chart types)
=============
A similar reasoning applies to pie charts as for bar charts: NEVER use
more than 5 colour-groups.
However, pie charts often have more data groups, therefore sometimes a
different solution is needed:
C1. 2 data groups => NEVER draw a pie chart with ONLY 2 segments (as the
second segment will always be (1 - first segment))
C2. 3-4(-5) data groups: use of 3-(5) different colour groups is
possible (though alternatives are equally effective)
C3. more than 5 data groups: this is tricky; obviously we can NOT use a
monochrome drawing.
HOWEVER, more than 5 different colour groups is a strong NO. Instead,
use only one colour group (rarely 2), with:
- slight hue-variations (NOTE: the next version is better)
- *contrast/luminosity* changes: 2 adjacent colours should have very
different luminosities, so that black-white printing looks OK and also
viewing in colour highlights the difference.
IF there are more than 8-10 groups of data, the user makes something
wrong!!! Some of the groups should be contracted into a single group.
Also, with more than 5 colours, some of the colours are chosen as
*shades of gray* (+ sometimes the colour black). This fits in the
concept of only luminosity changes (with sometimes colour saturation
changes).
An example will be presented from the WHO report.
Other charts (like line and dot charts) bear similarity to the pie charts.
D. DEFAULT EXAMPLES
===================
I have looked to the various chart styles on the voting page. Some look
interesting, though NONE looks really professionally. If I was to choose
from the available, I'll probably prefer the last one (number 12, blue -
yellow - for which I actually voted). This is the only one to have a
professional look. All multi-colour styles just don't seem right. Please
NOTE that even this one fails for the bar chart: there are simply to
many colours. Instead use either a single colour or only 2 colours
(whith the second one to highlight only important parts of the bar chart).
Various other professional examples from WHO reports will be presented
in a second writer document attached to the previous issue.
CONCLUSIONS
============
a.) *multi-coloured charts* actually never look professional
IF the chart contains many groups of data, instead of using dozens of
colours, consider:
i.) a *single colour* (see attached Chart_Bars_Styles_Blue.jpg)
ii.) a limited number of similar colours + shades of gray (see examples
Chart_Bars_Styles_Orange.jpg, and most other examples)
In this latter case, consider using the highest contrast colour-pair to
highlight only the important aspects of the chart. Therefore, it is
really NOT important to have dozens of colours, BUT rather a limited
number of them and use them appropriately.
b.) there is a huge difference if somebody draws a chart only with 2
groups of data (high contrast might be OK in this case), 3-5 groups
(medium contrast and optimal colour spread) or > 5 groups (various
shades/hues of same colour interspersed with gray tones). Having more
than 5 completely different (widely differing) colours looks awfully.
c.) As a last note: I would prefer more than one colour scheme. As
pointed previously, different schemes for the BAR and PIE charts, as
well as the 2 groups case, 3-5 and >5 groups case is also warranted.
Cheers,
Leonard Mada
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