Can't help ya with the Humbrol and tamiya colors.
"Steel" usually means dark silver
Presuming a standard Luftwaffe paint job, your upper surfaces should be RLM 70 black green and RLM 71 dark green, with either RLM 65 blue or 76 light blue on the undersides. 04 is yellow for the fuselage bands and wing tips. 66 is dark gray for the cockpit interior.