Is it common for 250r waterpump shafts to get hot

[250rmanfmf]

Hey, I am disassembling my 250r motor for rebuild and noticed that my waterpump shaft was busted (good timing) I saw in a couple of places where the shaft looks like a rainbow which indicates it got hot. So I thought that it was just that one. I have a quick-change clutch cover that will be going on the new motor and that had the water pump in it too and that shaft too had rainbow color in the same place. a pic is below. Is this normal or does something need to be addressed? I want to make sure I fix this as I will have a lot of coin into this new motor and would like to take every step to make sure it lasts.

any help would be great
Thanks
Tyler
133222