Rich Text Box in-string formatting

Hi guys, probably a long shot here but I had some code a while ago, and lost a hard drive, resulting in the code being lost.

I've recently started a new project and there's some code that I'm trying to find. I had a Rich Text Box in which I was able to format the text inside the string using colour hex codes and other tags to format the text.
For example, I could write:
And a function would parse and format the text before printing it to the text box.

If anybody knows of any snippets that work like this, please let me know, as I can't for the life of me remember how it was done. Couple of examples below.

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