In SMF editor, when you set a color for a text, SMF makes it into an inline style:
[ color=red]Some text[/color] becomes <span style="color: red;">Some text</span>
When a SMF forum uses multiple themes, some of them may be dark, some of them may be bright. So a color in one theme can be unreadable because of these inline styles.
I'm suggesting that SMF keeps a list of these colors, and if the selected color matches, it converts them to a color class appropriate to theme css. If doesn't match, then inline style it is.