I have been investigating this for some time.
In tile of tags, i can change the tag font and color
but the sub-tag font always the same, which is pretty small on mobile phone
Assuming you mean these:
You can do it with CSS like so:
davwheat thanks a lot. that works!
shuo-ding You can mark that as the Best Answer or let us know that this is Solved so mods can add the tag.