Changing material with C# lags on Windows phone but not android

Hi.
I have a problem, I have some gui buttons that change the material on an object when pressed.

When playing the game on an Android device there’s no lag but when I run it on a Windows Phone whenever the button is pressed the game freezes for half a second and then works again. Do I need to change my code so that it doesn’t lag on windows phone?

I used to use this line of code to change the color:

renderer.sharedMaterial.color = Color.red;

but I changed it to this instead:

renderer.material = redMaterial;

No. Report the performance difference as a bug.