The research on Royal Purples is too incomplete to really predict what you will get. The claim is that a Royal Purple is the same dominant gray gene as the Pearl Gray's dominant gray gene. The difference that is known between a Pearl Gray and a Royal Purple is the Pearl Gray has the dominant full dotting gene while the Royal Purple has the recessive to full dotting but dominant over no dotting, partial dotting gene. The Lavender has two recessive blue genes and at least one dominant full dotting gene.I finally can tell the different calls for my royal purple guineas! But.... I can't keep track of who's making them lol. I only hear one girl at a time so maybe only 1 out of 5.... but my young grey and lavender both sound like girls. So if I have one purple, one lavender, and one grey females and all purple boys I'll get lots of lavenders? With some purples? I haven't looked into guinea genetics yet. I want one of every color someday!
I create Royal Purples by breeding a Coral Blue hen (two recessive blue genes and a partial dotting gene) with a Chocolate cock (two recessive buff genes, two dark shade variance genes and a partial dotting gene). Due to results from repeated breedings it has been shown that this particular Coral Blue hen has one partial dotting gene and one no dotting gene. Royal Purples produced in this manner have to either be due to a mutation or else the combination of one blue gene, one buff gene and the dark shade variance gene. This pairing produces Royal purples on too regular a basis for it to be due to a color mutation in my opinion.
Depending on what hidden recessive color and dotting genes your other guineas have it you might get mostly Pearl Gray keets and Royal Purple keets but it is not impossible to get colors that you are not expecting.
Good luck.