Weight group colors in vertices blend between their neighbors by going through the entire range of values between the 2 points

For example if a vertex has a 1.0 (red) value and one of it's neighbors has a 0.0 (blue) value, the face will show a rainbow interpolation going trough orange, yellow, green, cyan and finally blue

In certain situations where each of the vertices of a face have different values (like 1.0, 0.5, 0.75, 0.0) it will create weird intersections in the middle that look like there is a vertex there that doesn't exist

The problem is even worst when the wireframe is not displayed and we only see gradients of colors indicating vertex values that do not exist

The solution is to fix the color blending mode to simply mix between the 2 neighboring colors. This way it is very clear that vertices have values of 1.0, 0.75 and 0.5 and nothing in between.