I think you misunderstood what I meant with my latest suggestion, so let me rephrase.
I don't mean the color selection should be moved away from the account settings, but that it should be additionally within the account creation (adding new account through the wizard) screen. As both colors and account creation are one-time operations for each account added, it is pretty okay to show it within the account creation screen as well.
But that would not change anything within the "edit account" or "edit identity" settings. Those parts would remain as is. The colors can still be changed or modified there. Only the wizard screen would change with one addition. Here an example what it could look like
This way, the feature is highly visible and also takes alot less steps to configure.
Edit: As for trying several times to set up an account.. The most common reason would be if the username or password were incorrect. For as long as the set color does not change each time one presses on "prüfen" but remains so even if one changes the username/password entries above, it should be fine.