A shoot'em up needs a straightforward visual indication, which your plane doesn't seem to have, of what part of the player's ship is vulnerable (usually called the "hitbox", even if it isn't a rectangle).
Usual choices are the whole craft (in this case engine fires should be clearly marked as safe by transparency or flickering) or a small part of the fuselage around the cockpit (in this case genre conventions demand starkly different and often bright colours, not grey on grey).
Whatever your choice of hitbox, players will be grateful for unreasonable paint jobs and exaggerated highlighting.