You are welcome to adhere to the ideology that suits you. As a Black woman who is American, I use the one-drop rule that indicates that one drop of Negro blood makes you Negro.
I am not pure African. In my blood, I have native American. Still, I would am discriminated against in that way. If you do not think of yourself as Black, that is your right.
Colorism exists. It's not about it not being a thing. There is a difference in how people are treated whether that person is from India, Africa, Asia, Europe, or the Americas. This is the world we live in. How we will be treated won't be on how we see ourselves, but how the world sees us.
So thank you for reading but I respectfully reject your theory about colorism. It is something I have experienced and many people I know and love.