Additive blending. Only brightens colors. Black is neutral and has no effect..
Alpha
Alpha: = 0
Default. Normal alpha blending.
Multiply
Multiply: = 2
Multiplicative blending. Only darken colors. White is neutral and has no effect.
MultiplyAlpha
MultiplyAlpha: = 3
Multiplies the target by the source alpha.
Only the source alpha channel is used.
Drawing using this mode is useful when rendering to a textures to mask borders.
Blending operation when drawing