The only ones I have been successful on determining the boys from the girls as keets are with the buff dundotte color, as the girls are usually much darker than the boys even as keets. (Of course, I've been wrong a time or two on those as well!) I don't know of any way of telling them apart other than that until they get their "voices". If you listen very closely, you may be able to detect that slight "buckwheat" from the girls at a few weeks of age. Hopefully someone else on here has had more success with this or has some different ideas.
(If you lived closer to me, I'd offer to swap you for whatever you needed.....I'd love to have some royal purples!)
I figured lol but was hoping. Planning on selling them by us in a couple years if it works out. Knowing us I'll end up with some of every color lol