I have been creating a contact list in Google Sheets to continually add and update names, emails, organizations, etc. for work. I am often copying and pasting this information from other sources as to avoid typoes. I know I can paste as special, though at times I am copying and pasting a handful of entries and this would take more time than I would like. Is there any way to have a script automatically change the font styling of a cell (size, bold, background, typeface, etc.) if it doesn't match the default?
You can use macro that records your desired font, size, cell color etc. It's a script that don't need coding. You may check more info on this link
Tools > Macros > Record Macro
If I understand your question correctly, you don't need a script at all.
You can use Shift-Ctrl-V instead of Ctrl-V to match the target styling. I do this all the time. As long as you're comfortable with keyboard shortcuts, it's significantly faster than doing Edit > Paste special > ... - in fact, just as fast as regular Ctrl-V :)
You can also paste stuff in however you normally do, and then use Ctrl-\ to undo all formatting (at which point it'll just be plain Arial 10pt, or whatever), and then bulk change afterwards, once you've cleaned up the text -- at first glance this option doesn't really answer your question, but I've found that in some cases the first "cleaning-up" of data after it's been pasted in can be easier to do with a bare bones look.