I believe this is not true. ID can be changed if you have Nitro. You need to buy nitro to be able to change the ID. The unique user id is longer: like 589473379990222325

Username color
Scammers can change their usernames, but they can not change their colors, which show roles of users in Discord channels. For each project, developers will asign different colors for different types of users: from admins, moderators, community managers, bots, and normal users.
Users that have important roles, such as admins, moderators, community managers, for example, usually have special colors, that are easily to recognize.



There is one id on discord that is unique and you have to enable developer mode in discord settings to get it.

Discord has option to check unique user ID. You need to enable developer option in settings to get this. User can easily copy Name and avatar of another user but cannot duplicate user id. If you compare user id you will get info if this user is the one that he is claiming to be. Just click copy ID as on image bellow and compare both ID's.



Also username color is not relevant in this case. As you receive PM from scammers username color is always the same regardless of users role on the official server.

I wrote some ways how to spot a scammer on telegram or discord here:

https://bitcointalk.org/index.php?topic=5167602.msg51908476#msg51908476