Last 13 characters of error output in 'C# Interactive' window are not colored red

[tmat]

Moved from dotnet/roslyn#63317

Version Used: VS 17.3 (Roslyn 4.3.0.3-22401.3)

Steps to Reproduce:

1. Open the "C# Interactive" window in VS.
2. Submit any statement that results in error diagnostics.

Expected Behavior: All error diagnostics are colored correctly (red).

Actual Behavior: The last 13 characters are colored black, while the rest is colored correctly.

This does not affect csi in the console, which is always colored correctly.