This is what felt natural to me, but multiplying it turns it greyscale:
What’s the correct way?
Use the color mix node set to multiply. Mix your texture with an rgb color set to be brighter than white. (If you click on the numbers in the color mixer, you can enter a number bigger than 1).
There is supposed to be a strength control, but it seems like it didn’t make it to version 2.80.
Note that yellow colored nodes are always meant for color and grey ones for value only. So you basically converted your rgb colors.
The other workaround until the updated principled node would be to add a mix or add shader behind your principles shader and rhere you mix in an emission shader. There you have simple strength control
Thank you for the very detailed answer!
I will use an emissive shader until the standard one is updated for 2.81 then.