It's a great moment when they can reach the taps. It's a celebratory moment, like when they can reach the doorknobs or light switches. It makes them just that much more independent.
Caspar has been able to reach the taps for a while but not enough to fully turn them on and off, meaning he always needed assistance. But now he can use them completely independently. With our cold weather we have also turned up the temperature on our hot water system. So right now it is really important that he knows which is the hot and which is the cold tap.
A couple of years ago a Montessori blogger posted about the same thing. They tied a red ribbon around the hot and a blue ribbon around the cold tap. I simply used coloured dot stickers and covered them with contact to make them splash proof. I am sure they won't stay on forever but I think it will only take him a week or so to get it.
To see the rest of our bathroom visit a the previous post Child friendly bathroom.