<p>Guys, can someone give me a brief run through of how to change the background colour of a CEdit control at runtime? I want to be able to change the background to red if the field is zero length and the normal white otherwise.</p>

You cannot do it with a plain CEdit, you need to override a few bits.
Implement your own ON_WM_CTLCOLOR_REFLECT handler, then return your coloured CBrush in the handler:
(roughly, you'll need to put the usual resource management in there, rememebr to delete your brush in the destructor)
```
```
class CColorEdit : public CEdit
{
  ....
  CBrush   m_brBkgnd;
  afx_msg HBRUSH CtlColor(CDC* pDC, UINT nCtlColor)
  {
    m_brBkgnd.DeleteObject();
    m_brBkgnd.CreateSolidBrush(nCtlColor);
  }
}
```
```