If you have to make a quiz like that you are uncertain of your own skills rather than the others.
Maybe you should read about the topic and learn.
If you have god skill in a field you know if the other person is real or not.
And you are not afraid to ask him to explain himself.
Not sure I agree with the color code as a test--that's more a test of how long they have been around, and how good their memory still is!
I've been in this business a long time, haven't needed to use or know the color code since way back when. So even a good, but newer, engineer would fail the color-code test, IMO.
That's a good hardware engineer design question. You could come up with those types of questions for RF, digital and analog engineers. These days, if the board design is no good, it's not going to work.