The tool allows you to easily change texture colors.
Wes McDermott, the Creative Producer at Adobe, has demonstrated how the UV Random Color generator can add variation to textures in Substance 3D Painter. It generates a mask based on UV shells that you can modify with an HSL filter. You can just click the Random button to quickly change the mask.
Apparently, many users don't know about this feature, so make sure you check out McDermott's ArtStation to learn more about Substance 3D products. You'll also find some awesome projects from the artist there.