Fixing openCV + Swift mobile app

I have a mobile app which uses open CV to change color of a wall. The problem with the algorithm is that it paints a wrong color. it mixes the color on the wall together with the color that has been selected by the user. I want it to only paint the color selected by the user.

https://apps.apple.com/us/app/rainbow-paints-visualizer/id1554758988

that is the link to the app.