One or another of the main model paint suppliers - it may be Tru Color or ScaleCoat - makes a couple of passenger interior wall colors, one cream/beige and the other green. Both are basically solvent-based paints. For things like seats, tables and the like, I prefer a standard acrylic, preferably sprayed on, to get an even finish that dries fast. I have used one of Tru Color’s auto model paints for this as I wanted a particular color but it is relatively pricey and won’t work with other brands’ thinner.