i've read that too... many web-sites/grow video's say you can tell by colour and by size!! personally i'd grow whatever colour the seed may be.. i'm not racist!!!
=) well only way u can tell if its female or male is to put it in flower and bout 1week of 12/12 ur gonna start seeing preflowers. hairs =female, balls=male
now im pretty sure the only thing u can tell by color of the seed is the maturity of it (white not so mature, browner with veins more mutare) the only REAL way to tell is flowering!
Figure on about 6 wks of growth from seedling to tell .
Part of the Fun is planting seeds and seeing what you get .
not all seeds germinate no matter what color, stripes, size they have