wondering if there is a "blend"as defined below mode

[Stephen Lefty]

Imagine there is a red square and yellow square, touching.

If the floggo (imaginary or existing brush) brush is drug straight the color difference. That would create a gradient from Red to yellow with orange in the middle. If not drug straight down the color difference would be weighted to the side the brush where on, shifting the red side with less weight to the yellow and visa versa. Is there should a brush or a way to do that?

 

This is would I trying to do: I have a green and part of it is in the shade. I would to somehow blend the color line so shade line is gradual and not sharp. Ideas.

[firstdefence]

Which App are you using and any chance of a screenshot?

In the meantime there is the Paint Mixer Brush in Affinity Photo.