colors in E-prime

[Svetlana V Gromenkova]

Hello,
Did anybody make any experiments with colored objects?
I need to present objects with four different colors, but I'm just
unable to find/create four colors which would be equivalent on all
characteristics  (luminance, brightness, etc.) and still be readily
distinguishable from each other. Besides, they should be easily
perceived even when presented at a rate of 100 msec.
The best I could find is white, yellow, black and blue on a grey
background, but honestly only white and yellow are good. Black and blue
are less prominent, because darker.
If anybody had colors in their experiments, I would really appreciate
it if you could tell me which colors you used.
Thank you.
Svetlana.