Goro Fujita gave me some homework . I was to create 4 cubes with a white stripe from imagination with no reference in different lighting settings. These are the cubes he suggested.
3. night with a few fireflies around it
4. rainy night (light coming from street light off frame)
And here is the result.
I did a similar exercise in the past with sheep. I think I've improved :)
The old sheep exercise can be found here <--