The mode-line can become rather complex -- e.g., powerline, etc. Answering a mode-line question is somewhat like opening a "Pandora's Box" due to the seemingly endless combinations users may have in their own setup.
This answer only deals with the
minor-mode-alist component -- the lighters are green and the mouse-over is red. The
'face property can be changed to whatever components are supported -- e.g.,
:foreground "yellow" :family "Times" :height 180, etc.
(setq mode-line-format (list
`(:propertize ("" minor-mode-alist)
face '(:foreground "green")
mouse-face '(:foreground "red")
help-echo "Minor mode\n\
mouse-1: Display minor mode menu\n\
mouse-2: Show help for minor mode\n\
mouse-3: Toggle minor modes"