I want to dye a lemon cake orange and dark blue.. do I follow the normal directions or add another color since the cake is yellow? I only have one shot to do this so that's why I'm asking for help.
I don't understand exactly what you're asking. If I were going to color a cake orange and blue, I'd put orange gel food coloring in one part of the batter and blue gel food coloring in another. You could either put the two colors together in one pan (although you might get a little band of green where they mix) or you could make one layer orange and the other blue. Does that help?
I doubt you will be able to make a yellow cake blue.
You may have been better flavoring a white cake with lemon flavor. I'm not sure you can really get a true blue using a yellow based cake.