Dynamic Texture with dynamic colors

Hey,

Hopefully somebody can help me:
I created a dynamic texture to draw some lines.
Now I want to change the color, but if I do that my hole image will change the color.
I just want that my current picture has the same color/s as before. Only my new lines should get the new color.
Does somebody know how to reach this or just have an idea to solve the problem?
If you need some more information, just ask.

Greetings

Use a mask to mask out what you want to change color and what not.