The temperature of colours matters hugely in mixing, so a warmer orange mixed with cool blue will make a duller green, for example, than a cooler orange mixed with the same blue. Transparent Orange mixed with Ultramarine Blue makes a fab black as they are opposite colours but mix it with Prussian Blue and it makes a gorgeous foliage green. Letting the colours mix on the paper makes a different green from mixing them together in the palette and overlaying each colour as wet on dry glazes makes it different again. There is just so much variety in colour mixing it is somewhat mind blowing but also sooo exciting!