I currently have a General Controls T-90 thermostat and I want to switch that with a RobertShaw RS5110. My current Thermo is wired with a Green wire going to F a Black wirre going to C a White wire going to H and a Red wire going to M. There is no diagram for this configuation. Does anyone have any thoughts about which termiators to put the Green, Black White Red wires in?

Do you have a central heat/cool system? Most conventional systems use red to power the t-stat (r terminal), white to power the heating circuit (w terminal), yellow to power the cooling circuit (y terminal), and green to power the indoor fan circuit (g terminal). Sounds like your system has a black wire instead of yellow for cooling. If the new t-stat has rc and rh terminals, a jumper between them is usually required. Check the installation instructions for the new t-stat-is a "c" connection required? If so you may not have enough wires to establish a circuit between the t-stat and the "c" terminal at the furnace.