Senegals can range from light to dark, but it's probably your substrate too.
I have four Sens in the same tank and some still vary in color from one another.
bichirs can change their colours to a very high extent.
Take a senegal from a tank with a black substrate and place him in a tank with white substrate for 1 day.
It would look like a totally different fish. So my answer is there isn't such a thing as light-based. There is only normal and leucistic.