@Timo Thank you for bringing this to our community.
You may follow @aakulov s' suggestion for Hue. However, if this ask is about Cloudera Manager UI, Please try the following:
For Cloudera Manager Custom Header Color
The custom header color is used to distinguish different instances of Cloudera Manager.
CM > Administration > Settings(Scope) > Custom Header Color
For Cloudera Manager Custom Banner Text
The custom banner is used to display customer specific text in the header area.
CM > Administration > Settings(Scope) > Custom Banner Text
Bonus:
For Cloudera Manager Custom Information Assurance Policy Text
An information assurance policy statement that must be agreed to in order for a user to login.
CM > Administration > Settings(Scope) > Custom Information Assurance Policy Text
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Cheers!
V