Setting the current vertex-color brush color

Hi, I’m trying to add two buttons/hotkeys to Blender that will quickly darken and lighten the current color that Vertex Color mode uses when doing Set Vertex Color (Shift+K).

Basically, get the current color, alter it, set the current color.

I can’t figure out how to get/set this color though.

I tried the API call below, but it doesn’t set the color that Shift+K will use next:

 bpy.context.tool_settings.vertex_paint.brush.color = Color((1.0, 0.0, 0.0))

Any help is very appreciated, thank you!