how to modify the image container size

if you see the attachment, in grid view listing.. the image and the related store is visible in a grey color container..

my query is:

1. how can I decrease the container size, because it’s eating my lots of space for no reason.
2. how can I change the grey color to white.. (not sure if I will change, but will see which one looks better..grey or white).

Thank you 🙂