Discord is now slowly rolling out the ability to send colored messages within code blocks. It uses the ANSI color codes, so if you've tried to print colored text in your terminal or console with Python or other languages then it will be easy for you.
To be able to send a colored text, you need to use the ansi language for your code block and provide a prefix of this format before writing your text:
\u001b[{format};{color}m