Why yellow?

[TMD2003]

Indiana Jones and the Fate of Atlantis has a level that is all blue on black. Not cyan but blue! Nearly invisible on the typical fuzzy TV.

CORE did much the same - but the colours fade to ever-darker shades as the battery in the space suit runs down. If the screen gets to blue on black, you're in deep trouble.

[Sol_HSA]

In short, yellow simply looks better on RF or composite

This is the best answer I've seen so far. =)