TPO Charts can be setup to paint the TPOs of the day session a different color than those of the overnight session...as seen below...

In the standalone TPO Charts, user can split the day and overnight profiles by setting up as seen below with Special Duration of Split Session and specifying the appropriate day session.

At that point, separate profiles are plotted for the day and overnight session.  Users may then paint the overnight session letters/TPOs a different color by setting the config MPCustomOvernightColor to true, and then setting MPOvernightColor to the desired color.

Note : when using TPO letters (and not block), please note that another way to quickly identify the Overnight session is to set the Configuration variable MPLowerCaseOvernight to true so that every letter will be in lowercase....

A specific color for the Overnight Session can be also set with the Profile Indicator in Multi-Pane Bar/Candle charts as seen below...