I'd love to see the diffuse color of a material being displayed in the Blender's default solid mesh display mode, if that's possible, because only the old Blender renderer has this feature, while in Cycles materials you need to set a separate color swatch for viewport color display.
I'd like to second this request!
I requested this feature a number of months ago on the old bug reporting system.
Just having a hint of the material colour in the solid 3D view is really handy to separate out your objects. e.g. on a simple car model you'd have black tyres, grey wheels, and a colour for the bodywork. It's that simple.
Just a simple custom flat colour visual cue.
This would make modelling easier.
1. Default editor/"solid" color is some average of the diffuse shader color
2. Possible to override with user assigned color to make materials easy to differentiate while modelling
3. RPR global override that automatically assigns random color to all objects independent of material for ease differentiation while modelling