Change username

[AzureEyed]

I just installed wsl using the command
wsl --install
I was asked to choose a unix username, I did and now I want to change it, I couldn't find anything online on how to do it, I would apreciate help in the matter, also, what is the difference between the following command line prompts:
Ubuntu: username@pcName
Default: username@pcnName
I see that in ubuntu it's having a red background and I don't like it how to I start with the black one? (aka Default: username@pcnName)