>>So? Another form should not change ShowTips at runtime.
>
>It's a grid class that is used on the form. Why it can not change properties of its parent?

OOP principles. Objects should not directly change the internal properties of other objects. If something happens on your grid that is supposed to make the form change color, it should call upon a method of the form and ask it to change the color. It is wrong thinking to make the grid directly change the form's color property.