My sister's boyfriend painted this picture. I am not familiar with art and the only explanation I got is that it paints the light. I wanted to know more about the picture, but I don't know if it would be off-topic.
It depends on what you want to ask.
If you’re curious about what the technique may be, or the color scheme, these are things that would be helpful for someone needing to know the physical traits or skills needed to make another piece using those techniques. So, those types of questions would probably be on topic.
If you were going to ask about interpreting the image, then that would not be on topic. Although many of us love art and enjoy thinking about those things, this site is not geared towards that because it’s more discussion- and opinion-based questioning.