When you want to add dark tones on clear jerseys (in the hollows), you can use grey wash, but you can try other colors too.
Example :
light blue on white jersey
red on orange jersey
orange on yellow jersey
etc...
to obtain a smooth finish, try to wash only the hollows, not the edges. You can also add an final highlightning touch on the edges :
white on white jersey
orange on red jersey
yellow on yellow jersey
white on grey jersey
you can notice that the already light jerseys (yellow, white) don't really need highlights : just add a small painting effects on edges with the main color.
you can also add a little black lining (ink or diluted paint) between diferent zones (jersey+pants, jersey+arms, etc...)
you can also take a look on my skin paint tutorial here :
http://miniaturefootball.org/2010/01...-step-by-step/
hope it helps