Card-mod and new tags

Hi all, I have a markdown card with data elements for which I need 5 different colors, depending on their value
I am using card-mod for the layout and till date I (mis)used ‘span’ and ‘mark’ for that but now I need 3 more.
I thought to just add my own tags in the card-mod css but that does not seem to work.
Is this indeed the case?
What are your recommendations? Should I just take further standard html tags into the card mod and mis-use these as ‘strong’ ‘em’ ‘u’