Widget/ Sidebar background colour

Hey everyone, i’m relatively new to wordpress so apologies if this is a very basic task but the background colour of my sidebars are colourless i.e. it looks like the out of the box colour. The main body is white so you can see where the contrast between the two are. I am using Scoreline theme. I have been trying to insert code into the custom css but nothing seems to be changing. Thanks in advance for any help.