I can help. To change the account color on the Write Checks window or Register follow these steps
Display a check or register (Banking > Write Check or Use Register)
On the Edit menu, select Change Account Color
Choose a color and click OK.
Keep in mind once you've changed the account register color, there's isn't a way to change it back to the default color. I'm here to help if you have any other questions.
Your suggestion changed the colors on the check register, but not the highlight on the reconciliation page.
The current/default highlight on the reconcile page is a very dark green, and it's hard to see the black text beneath it. That makes it hard to read. Is there a way to change it to a lighter color?