FVWM: FvwmButton Color override Swallowed Conky

[for.register for.register]

Hi, All

I want to swallow conky into FvwmButton, but I found that
FvwmButton Color override Swallowed Conky. I mean, after
several seconds, conky figure disappeared, only leaved with
the blank buttons with the FvwmButton background color.

DestroyModuleConfig LaunchTime: *
Style *LaunchTime !Title, !Borders, Sticky
*LaunchTime:    Colorset 8
*LaunchTime:    Rows 11
*LaunchTime:    Columns 1
*LaunchTime:    (1x1, Swallow "xclock" `Exec xclock \
               -bg '#31658c' -fg white -digital  -strftime \
               '%a, %d %b %Y %H:%M'`)
*LaunchTime:    (1x10, Swallow "Conky" `Exec conky -d`)
Module FvwmButtons -g 300x550 LaunchTime


Thanks.