Blending face colours

Hi folks.

if I have 2 faces joined by one edge, both different colours (basic blender colours) is there any way to have the colours blend over the edge?

Thanks.

The only way I can think of is to blend the two colors in a photo file and then use UV mapping to apply that to the two faces.

Might be possible to do it with vertex colors. Setup vertex colors as grayscale for mix. Attribute node with vertex color name then controls material mixer.

Thing with this approach is that how smooth it blends depends on mesh density. Previously mentioned UV approach would offer far more control.