Me [painting bauble for reasons which are too dull to go into]: I wish I had more colours in this paint set.
Her: Like what?
Me: Well, purple. You can’t make purple from other colours. [Under my breath: Richard of York gained battles in vain]
Her: Is it possible that you are mixing up rainbow colours and primary colours?
Me: Um.
Her: Try mixing red and blue there and see what happens.