In the "OnGotFocus" event of the control, type in this code:
If Not IsNull(Me.CompanyField).Value <> Null then
Me.OtherFieldName.BackColor = Value Of Your Color
Me.OtherFieldName.Requery
EndIf
For the value of your color, do some research on RGB colors.
You'll have to provide a combination of 3 numbers here, one for each color. (There is another way to do this though, but maybe just as involved)
Have done this once, but let me know if it doesn't work and I'll spend more time on it.
edtab