I would like a feature that would allow me to ban specific colors that are close to invisible on plans. Both near-white colors on the white plan backgrounds and very dark colors when tracing black lines make it difficult to visually verify something was taken off.

I would second this. We have run into quite a few issues with this the past couple of days, to the point of needing to manually adjust most colors. I am not sure that it needs a customizable setting, but the default color/shading/opacity could use some work.
👍3