The RAlt key works correctly! That is, it works as an AltGr key to produce symbol layers, as it was intended to do.
However, you don't want that do you. You want things the standard ANSI way without those symbols that you think you don't need anyway, right?
Now, you didn't tell us anything about how you're using Colemak and we need to know that if we're to be able to help! Are you using Linux/XKB? MacOS? Windows? If the latter, with a MSKLC installer or an AutoHotkey script or my fancy EPKL program?
With EPKL, I could tell you how to get a so-called VK remap that'd allow you to use Colemak without changing the keys' functionality. As a bonus, you'd get the fabulous Extend layers and lots of other goodies if you want them!