I want to make a fun cake for my sons end of year baseball party.  I was thinking about making a chocolate cake and then putting fun colors inside.  I see all the post for the polka dot cake but I don't have one of the makers.  I am making a half sheet cake.  I want to do it chocolate and make the dots or what other shape in a vanilla flavor.  

I don't know if I cut out shapes if the chocolate cake mix will seep into the vanilla shapes?

Any advise or ideas are welcomed.

AMake the dots like you would cake pops. Make vanilla cake or cupcakes in different colors and once they have cooled, break it all up and mush it together. Make them round and put them in the chocolate.