Sorry mate,
Right - conventional aeronautical standard for markings general has any green range meaning 'normal'.
Broadly speaking (for yer RPM instrument) it will be marked from 500 rpm ('cos it's unlikely to run properly below that) right up until red radial. Thats the limit.
Some engines will have green then yellow then red line (TIO-360 Conti, for example, in the Seneca III) where the take-off power is not rated for longer than a certain time period (5 mins??)
Others will have a little band of yellow halfway along the RPM scale. Usually this is an 'avoid' range due to harmonic vibration. Engine slowly bashing itself to bits...
It is distinctly unlikely that carb icing will be associated with a specific RPM and that it will be marked on the tachometer.
There you go... any help?