Filter color fails if it the color is uppercased

[hjemmel]

When I added color like #41236D that is supported by Gmail API I get the following error:

Error: creating labels: creating label "AppSignal/Kickback": googleapi: Error 400: Label color #41236D is not on the allowed color palette, invalidArgument

If I do the same with the but lowercasing the color, the gmailctl apply command works perfectly.

Maybe it would be a good idea to lowercase the colors before send them to the API

[mbrt]

Gmail APIs accept only lowercase hex strings and I'm reluctant to relax the restrictions, unless there's a good reason. This is to avoid confusion and potential incompatibilities in the case Gmail changes something.

What I can do however is returning a better error message. You found the docs by yourself but it's not necessarily obvious to everyone, so I'm going to go ahead and do that.