I won't tell you because I hate people that post in non standard colors :evil:
Well sorry for being blind, all the white & gray is painful to the eyes.
Well, in that case, your trick will not work since you never need to read your own posts when everybody else is still posting in standard colors. In exchange, you've managed to make your posts hard to read for other users with some kind of color blindness. Great job!
Now, what would be great would be a way to customise the forum colors on a per user basis, instead of having a few fixed themes

Too bad phpBB doesn't have such feature out of the box though. But even then, a possible solution would be to install a custom CSS style sheet for the forum only. With that, you should be able to change the default colors easily.