The central part of the model was painted Flat White and the base sprayed with Burnt Metal Buffing Metalizer

The borders between the white and the green were masked with Tamiya masking tape. A narrow band on the third stage was also masked.

Green was sprayed on the bottom of the boosters and the top of the rocket. Following this, "Post It Note" masks were stuck to the booster.

Green was then sprayed on the main body between the boosters...

...resulting in a clean demarcation line on boosters and body.