I was trying to type f2f2f2, but I can only type f2. The moment I try to type the second f (like f2f) it reverts to ff22ff automatically. This happens on both the Color and Text Color when trying to create a new category (or editing it).
Thanks for the report. I can repro on Meta too. Furthermore, it is impossible to delete what you were typing using the back button on the keyboard.
As a temporary workaround while we resolve this issue, you can copy paste the hex value directly into the field.