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
\u001b is the unicode escape for ESCAPE/ESC, meant to be used in the source of your bot (see ). If you wish to send colored text without using your bot you need to copy the character from the website.