How to set Powershell Color scheme permanently

Its possible that you are setting the colour properties in the wrong profile.

PowerShell actually has 6 profiles to chose from:

Current User, Current Host - console: $Home\[My ]Documents\WindowsPowerShell\Profile.ps1

Current User, All Hosts:$Home\[My ]Documents\Profile.ps1

All Users, Current Host - console: $PsHome\Microsoft.PowerShell_profile.ps1

All Users, All Hosts: $PsHome\Profile.ps1

Current user, Current Host - ISE: $Home\[My ]Documents\WindowsPowerShell\Microsoft.PowerShellISE_profile.ps1

All users, Current Host - ISE: $PsHome\Microsoft.PowerShellISE_profile.ps1

Please try and set the profile colouring in the all users, all hosts profile to see if the settings persist. If it does, then try modifying for your various profiles as a user to get the configuration you want.

for more reading on PowerShell profiles (source for this answer) - see https://blogs.technet.microsoft.com/heyscriptingguy/2012/05/21/understanding-the-six-powershell-profiles/