Legal Question in Civil Rights Law in Washington

I'm confused - why would that be illegal?

The only thing I can think is that you live in a deed restricted community which will not allow black curtains to show through the windows (visible from the outside) and only allow a certain pallette of colors visible from the outside. The remedy for that is to hang an acceptable color curtain first (facing outside) and then hang a second dark curtain (facing inside).

I'm not a WA attorney, but I was curious about your question. Please elaborate or see a WA attorney for help.