Nothing is one color. Nothing looks the same all the time. Memory and thought sometimes seem to still things — to solidify them. But the things themselves are always changing.
You can make the light even when you paint to give yourself more painting time. It’s a very practical thing to do: to paint in artificial light. But the painting once it’s finished will be seen in all kinds of light. And it will look different in the morning, and it will look different at night.