Background colour of form controls

[Pat]

From a database i have inherited, I have noticed that any forms background colours are white until the cursor is put into the control when the background changes to yellow?
This doesn't happen for all controls though just the majority.
There is no code to change this background colour or at least i cannot see it.
Can anybody shed some light?

[JohnH]

This question has been cross posted and answered here- it was done using Conditional Formatting.