In that case... use the function above and this code.
It darkens the form once...
VB Code:
  1. '''in a button click

  2. Me.BackColor =darkencolor(Me.BackColor)

  3. Me.ForeColor = darkencolor(Me.ForeColor)

  4.  
  5. Dim X As Control

  6. For Each X In Me.Controls

  7.    X.ForeColor = darkencolor(X.ForeColor)

  8.    X.BackColor = darkencolor(X.BackColor)

  9. Next

  10. '''