Please see the photos for before and after.
It is very strange, but it might have to do with a mirgation I did a while ago from trail to production.
I can reload a old version but it would result in me loosing work. And I can go physical edit each one, It just the second time it has happened to me now!
Could you please share more details about the error message within your app?
Do you create an app based on your CDS Entity on your side?
Further, is the 'Number of Colours' column a Option Set type column in your CDS Entity?
Currently, within PowerApps, there are some updates on CDS capabilities (including Option Set type, LookUp Type, .. etc). More details about these updates, please check the following blog:
On your side, please consider take a try to turn on the "Relationa data, option sets, and other new features for CDS" option within the Advanced settings of App settings of your app, then re-load your app, check if the issue is solved.
Please consider take a try to fix your issue through the blog I provided above.
If the issue still exists, please consider take a try to re-create a new app based on your CDS Entity, check if the issue still exists.