Change of background colors in portfolio

Hi there,

I don’t know if this is out of support scope, but I would like to find out if it’s possible to change the background of the portfolio on home page or not.
Screen shot of where I mean is at https://imgur.com/0rWt5k1

I would like to change the background to become: https://imgur.com/eyyZiUx which has a grey background.

Can I use custom css please?

Thank you,
Johnson

Ticket