doc/docs/en/shared/blend-modes.md

The Blend Mode property defines how the component graphics should be blended with the graphics behind it. These are the available blend modes and how they are calculated:

Alpha : Normal blending: src.a * src.rgb + (1 - src.a) * dst.rgb

Add : Brighten the background with the color values of the corresponding pixels of the component: src.rgb + dst.rgb

Multiply : Darken the background with values of the the corresponding pixels of the component: src.rgb * dst.rgb