I think your blue one is a boy and the yellow one is a girl.
But since it's easier to see if you actually look at the parakeets in real life, I'll give you the article which tells you all about how to tell the genders of baby parakeets, so maybe you'll be able to tell better.
Here's the link:
By the way, in the beginning of the article right under the heading it'll say "Photo of baby budgies." Be sure to click on that, and look at the difference in ceres. It will help you understand the information in the article better.
Last edited by Irishku; 08/11/09 08:51 AM.