:-) The easiest way is to mask the outside of the cockpit parts, then paint them the interior colour first (this colour will show through on the inside. Attache them to the model and paint the exterior colour, when you paint the rest of the model. Sometimes it is possible to mask the inside of the canopy and paint the interior colour on the inside, this is obviously the better option but, unless the parts are flat or large, as in your pic, it is almost impossible to do. The first option is easy and works well.
Mal