regarding the data structure the font for Action texts is not scriptable... which doesnt mean it is temporary changable.
you could try to link to another Font via Lua.
InterfaceActionTextFont
or
GameActionTextFont
are the needed fields depending if your action text is configured in the game settings or inside the interface.
e. g.
game:setValue(VGameActionTextFont, Fonts["fonthighlightname"])
untested though