Probably a hilarious story

Tale as old as time.... no, wait. Tale as old as paint and coffee mugs.

If you are not looking down to be able to see which is which, you are not looking down to be able to read the mugs.... this would probably only be useful if the water gets waaaay nastier to the point you can’t tell them apart by looking

You'd be amazed how often I have dipped my paintbrush into a fresh cup of tea

I would say instead of that, he should just use different colored mugs, maybe different sizes.