The most obvious thing that I can see is that you are updating the property
Color_Background
however you are retrieving the form's own
BackColor
.
You need to change this:
richtextbox2.BackColor = cp.BackColor;
To:
richtextbox2.BackColor = cp.Color_Background ;
Also, this may also need changing:
lbl_ColorResult.ForeColor = Color_Foreground;
lbl_ColorResult.BackColor = Color_Background;
ChangeTrackbarValue(BackColor);
To:
lbl_ColorResult.ForeColor = Color_Foreground;
lbl_ColorResult.BackColor = Color_Background;
ChangeTrackbarValue(lbl_ColorResult.BackColor);