Hi Lenny,
I hope you are talking about Userform textboxes. Then you can use this
in the Form code:

Private Sub TextBox1_MouseMove(ByVal Button As Integer, ByVal Shift As
Integer, ByVal X As Single, ByVal Y As Single)
If UserForm1.TextBox1.Tag = 0 Then
UserForm1.TextBox1.BackColor = &H80FF& 'the changed color
UserForm1.TextBox1.Tag = 1
End If

End Sub
Private Sub UserForm_MouseMove(ByVal Button As Integer, ByVal Shift As
Integer, ByVal X As Single, ByVal Y As Single)
If UserForm1.TextBox1.Tag = 1 Then
UserForm1.TextBox1.BackColor = &HFFFFFF 'the regular color
UserForm1.TextBox1.Tag = 0
End If
End Sub

If you want to change color of the Textbox from Drawing Toolbar then I
can´t help you.