What color do you get?

Blue and yellow are two of the primary colors, and mixing them together makes green, since blue paint absorbs most colors of light except blue, yellow absorbs most except yellow, and combining the two leaves mainly the green wavelengths reflecting back to your eyes.

Purple comes from mixing red and blue instead, and orange comes from mixing red and yellow, so neither one is the result of combining blue and yellow specifically.

Red, blue, and yellow are called primary colors because you can mix them in different amounts to create almost every other color, but you can't mix other colors together to create them.