If these are data validation dropdown lists, you can't change the font
size. There are a couple of workarounds he

http://www.contextures.com/xlDataVal08.html#Larger


wrote:
Anyone know how to increase the type size in an Excel Drop Down List.
Currently, the text in the form's Drop Down lists appears as to be
approximately 6-8 pts. I need to increase the text size to 12-14 pts so
clients can read the drop downs easily and make their selections accurately.


--
Debra Dalgleish
Excel FAQ, Tips & Book List
http://www.contextures.com/tiptech.html