For regular every day in calls, I use a little mascara and red lipstick. It's quick to reapply and touch up for a few moments between sessions. I like to keep my schedule tight, especially on my high volume days, so I like low maintenance.
If I have a dinner date or longer engagement with a regular, I get more sophisticated with makeup (and appearance in general) as they are paying me to have more prep time for the model look. I'm happy to wear no or almost no makeup though, and some of my regulars prefer this. Either way, it's important to use makeup that doesn't rub off. Last thing I need is a regular client with makeup on his skin rushing to a meeting or to a wife/gf after our session.