Sometimes when I come in from painting outside my piece will look grayer or more muted than it did outside. I do have a natural bent to painting darker ( I think everyone has a tendency to paint lighter or darker) plus the light is so different inside than out. The light here in the Sonoran Desert is so intense and I think I'm painting with saturated or cleaner color and I'm not. So, since our work is viewed inside instead of outside I'm adjusting my color mixing slightly. I'm keeping my colors a little stronger outside, not much but enough so that when I go inside they tend to read better. I'm not using as much of the compliment in each mixture. I still paint what I see ( to some degree, its more painting what the light is doing instead of matching color) but with a little more caution in mixing each color.