The Tint tool allows you to paint onto strokes point mixing the material base color with a selected vertex color.
Selecting a Brush, Color & Mode¶
In the Tool Settings select the brush, color and mode to use with the tool.
You can configure the brush main settings exposed on the Tool Settings for convenience. For the vertex paint brushes configuration and settings see Vertex Paint Brush.
Ctrl-LMB erase the vertex color.