Hi all

I am wanting to create a similar molecule as 

https://en.wikipedia.org/wiki/Chemical_polarity

showing the red/blue surface corresponding with partial charge of the atoms. 
I have a drawn an H2O molecule. From what I have learned from the help, I should go to Display - Style and then chose 'by grid'. However, this is greyed out. I tried to add several types of surfaces (Structure/surface), but I never can tick the 'by grid' option. 

Could anyone help me with this ?

Regards

Diederik D'Hert