error messages

[Harish Babu]

Hi all,
  Whenever there is invalid input in the form,iam able to show all the error
messsage at once ,instead of showing all the error messages ,i want to
change the color of the labels corresponding to those fields which has wrong
input.For eg. the lables of the invalid inputs should be red in color and
those with valid input should be black ,when iam showing the form for second
time after validating the user input.How do i do this ? Has any one tried
this ?.Any help is appreciated