Disable Material Glossy Lighting (Show Weights)

Haven’t found a solution online so I’ll ask here. I’m in the process of assigning vertex weights specifically to different vertices using the “show weights” display. However, the material’s glossy lighting is getting in the way, making the whole warm/cold color palette a mix of either being too dark or blurred by light. I’ve imported a model into Blender and noticed that its model doesn’t have this issue and the weights pop out on a flat surface while still remaining illuminated when show weights is turned off, but I can’t find any differences in the settings. Checking shadeless doesn’t seem to help (and only affects other objects not showing weights). It isn’t enough to hinder my work but it’s a real bother to work with.

In 2.80+, look at the Shading dropdown for your 3D viewport. Change it from “studio” or “matcap” to “flat.”