One thing I always try to tell students is to try to arrange your paints the same way each time you work. This is my (current) working palette. I always keep the blues up at the top, but I put ultramarine next to burnt umber before I head to the reds/pinks. Mainly because that's my favorite way to make gray. I then round the corner of greens, then yellows and white is always to the far right with radiant blue right above it. Why this way? Mainly because that's the way I've always done it. When I go to mix or use a color, it's right there. Being consistent saves time. Happy Painting!!!