It took 5 fully colored pages before I started feeling a direction for colors. Once that was done, I had to go back and recolor those 5 pages which was hours of work, but well worth it. And now, laying down flats is breezing by.
So if you ever decide to give coloring a shot, here's a (rather obvious [but not to me]) tip - decide on a color palette first. Experiment all you want until you get there (that's what I did), but get there. The whole thing will feel more balanced and complete and also move faster.
This is part of the palette I've chosen.