Problem with paintbrush tool

[Joy1776]

Thanks in advance for any help. I am trying to colorize b&w photos with the paintbrush and transparent colors. When I stop and start again the color goes on darker on the areas already painted, which messes the whole thing up, as seen in the attached photo. It's challenging to do a larger area continuously and impossible not to overlap when restarting. What do I need to do to have consistent color when I stop and continue over an already painted section?  

[MJW]

I think it might work to change the Blending Mode from Normal to Overwrite. (The Blending Mode for the Paintbrush is at the right side of the toolbar, with the beaker icon.)

 

If you're not already doing so, you'll need to paint on a separate transparent layer, above the picture layer. I think the proper Blend Mode for the layer is Multiply, since that corresponds most closely to how transparent pigments behave.

[Rick Brewster]

If you're using the Alpha value in the Colors window, try this instead:

 

Leave Alpha at the full value (255). Create a new layer. Set the layer's alpha to what you were using for the color. Now, draw on that new layer.

 

This also has the benefit of being non-destructive. You can hide/unhide the layer to see before/after.