Hexadecimal numbers are a common way to represent colours, he can probably copy paste the colour numbers back and forth between code and an image editor. Using

Hexadecimal numbers are a common way to represent colours, he can probably copy paste the colour numbers back and forth between code and an image editor. Using an existing image editor as a level editor must save time. It would get more complicated when you want to reference a specific thing on the map, eg particular behaviour for this locked door.