Moodle Atto HTML-editor has no options to change font or font color, but it has other good features that make it the default editor (auto save, voice and video recordind (max 2 minutes), etc..).
If you need to use font colors in your Moodle course, you can change your editor in your user setting (editor setting is user-specific).
Click your user icon in the upper right corner and select Preferences.
Select User acount -Editor Preferences
Select Text editor: TinyMCE HTML editor and Save changes
Now you have TinyMCE HTML editor selected.
Clicking on the first button will open the toolbar and the buttons for changing the font, font size and text color will appear.
First, select the text you want to format and then select the action.
You can change the Default (Atto) editor back to you in the same way.