TL;DR
Paint-able belts (all) to make them easier to tell apart in complicated setupsWhat ?
This would have only cosmetic effects on the belts but help to organise them. Belts can be recoloured to visually distinguish them. The 'paint' comes off when the belt is removed. Note that this does not affect the default colours when placing, it can instead be painted over in the way a tier 1 belt can be easily supplanted with a tier 2 while keeping properties.Belts as of current
.
With added colour (Photoshopped)
Why ?
WHY do you think it increases the value of Factorio as a game?It would help players keep complicated setups of belts organised and trace which belt feeds where.