Css of “Your Profile” editor in users admin section

All of the admin CSS is in wp-content/wp-admin/wp-admin.css, wp-content/wp-admin/rtl.css, and in the files inside wp-content/wp-admin/css. I’ve never edited anything but wp-admin.css though (and rarely) and it will save you trouble on upgrade to just add your own css file via the admin_head or admin_print_styles hooks.

Got it! Thanks a lot for the guidance!