Sheer neutrals are the most professional. Soft pinks and milky whites work well (OPI Bubble Bath is a classic), and a taupe or greige never looks out of place in a meeting. A deep burgundy or navy can look just as polished if you’d rather go dark.
I use Essie Ballet Slippers when I need to look pulled together fast. Clean application matters more than the exact shade. Chipped polish in any color undoes the whole effect. If you only want one bottle, get a rosy nude one shade deeper than your skin tone.