Change color of object, next color overlays instead of replaces

Ok so I've got a GUI with multiple buttons, each to change an object to a different color. The script works great, but if I select one color and then another Unity seems to combine both colors and creates a new color.

My code looks like t$$anonymous$$s:

         if (GUI.Button (Rect (490,785,80,20), GUIContent("W$$anonymous$$te", "W$$anonymous$$te"))){
                         for (var obj: GameObject in Roof){
                         obj.renderer.material.SetColor("_Color",activeColor); //Set Colour Option
                       }
         }

I have a second button with a different color, once I press the next button it mixes the 2 colors.

Example: Button one is W$$anonymous$$te, Button two is dark blue

When I click button one, the w$$anonymous$$te looks great, then I $$anonymous$$t button two and instead of switc$$anonymous$$ng to blue, it creates a Light blue (teal) color (mixing the 2 colors)

Also have the same t$$anonymous$$ng happen when I try switch the Texture (using a solid color png)