Hi @jirimeijers,

I am actually a bit confused on what you want to do here. In your screen image, you are showing the Index colors (1-255). These can't be changed to a True Color. However, any index color that is displayed on the screen can certainly be mapped to a true color in the plot style.

I made a quick video that shows how to modify a CTB file with one color (Red #1). Instead of having it plot to Object Color, I select the True Color value that you indicated. Is this what you are trying to do?

Please select the Accept as Solution button if my post solves your issue or answers your question.