Mixing blue with red make purple. Right? The answer is sometimes. Depends on the exact blue and red you use. It also depends on the percentage of each color you use to achieve the exact color you are looking for.
This is an example of how two different blues and two different reds can produce very different colors when mixed together in different proportions. I'm using watercolors here but you could do the same thing with oils and acrylics. I could spend the whole day exploring this topic. Because the study of color is really infinite.
As a fiber artist, I use fabrics and threads that are manufactured by companies — not created by me — but understanding why adding a brown, blue-green, or rust to a piece I'm making with red and blue fabrics can make a pleasing combination, can give me a new perspective on how to use color to make good art.
Think I'll spend tomorrow seeing what combining yellow and red will produce! (Yes, the simple answer is orange but I bet I will find some interesting surprises!)