Tex Murphy Tesla Effect

Great to have Tex back but now I'm stuck.
Day 9, Level 4, Routing Power Cores.
I understand the right and left columns and the up and down
but how do I get to the one I want to change
and not lose the ones that are already correct.
What am I missing ??

I have not played the game.
The walkthrough. Has a step by step.

I might be misinterpreting the walkthrough but it states that you do it by column. Will doing the game by column work?

After playing Whack-a-Mole with colours and columns for several days
I realized that I had to go further back in the game to reset
the puzzle.
thanks for trying to help.

On with game.

Enjoy the rest of the game.