How to remove unwanted block at bottom of portfolio page (not the footer)

Hello!

Having a design problem that I can't work out how to fix, and would be really grateful for your help...

Is there a way to remove the block colour band at the bottom of the page (that's not the footer, it seems to be part of the block above), that only appears when my website is viewing in either too small or too large sizes? I would like the background image to stretch to the full length of the page, no matter what size I view it.

I can't find a way to do this, in either the site styles or edit section, so wondering if it needs to be a code injection... could someone please help?

Thanks so much!

Worked perfectly, thank you!