PUZZLE 088 Neon Lights

Here we have some neon signs.
One of the three signs is still not switched on.
Each sign contains two letters, which are lined up in a uniform way.
What are the letters on the third sign?
Enter the letters in the two boxes.

Hint 1

Try dividing up the shapes on the signs.

Hint 2

What could be the letters displayed on each sign?

Hint 3

Try cutting each sign in half vertically.

Super Hint

You can figure out the letters on the third sign by following on from the letters on the left.

Answer for 'Neon Lights'

The answer is 'GH'.