Analog Thermostat Wiring Slant/Fin Sentry S-34 And S-60 Gas Boiler For House Heating. Need Help With Drain/bleed. Thanks,?

Slant/Fin Sentry S-34 and S-60 gas boiler for house heating. Need help with drain/bleed. Thanks,? - analog thermostat wiring

Moreover, opened with an analog thermostat. It has a brown wire and a yellow wire. With a digital thermostat (RiteTemp 6022), has a large number of terminals. Most are like the two terminals that are used, W - the heating and HR - heat output. But certainly with a wire that goes to the terminal. (Is there a standard brown or yellow, if the possession or control). Any information is helpful. Thank you!