"White" can be described as having various shades or depths, ranging from pght to dark.

For example, you could say:

"The white paint on the walls gradually gets darker as it goes from the top to the bottom."
"The white dress she wore had a gradient effect, with the color becoming gradually deeper from the top to the bottom."
"The white icing on the cake was a bit pale, but it got progressively darker as you moved further down the layers."