Colour blindness vs water dispenser

Today at work, my colleagues and I were talking about colour blindness right after lunch break at the pantry.


Me: Eh, Raf, you got colour blindness kah?
Raf: Yes, unfortunately.
B: Yeah.. he has. You didn't know kah?
Me: No I don't. How bad is it?
Raf: Very bad...!
B: (while filling in his water bottle using the water dispenser) Okie, tell me. How can you tell a difference between "Hot" water (in red) and "Cold" water (in blue) tap. (pointing at the dispenser)
Raf: Well.. first of all, I can read. H-O-T for hot water and C-O-L-D for cold water.
B: Puzzled. Look at the water dispenser, face turned red. Embarassed! And said "Okie, everyone let's get back to work!"