Transparent backgrounds for blog page

Is there any way to and a slightly transparent background to the scrollable area and primary sidebar on my Blog page (Please see attached picture: https://www.icloud.com/#iclouddrive/0-QmRW3_x-bMTg_CNTubczTyQ ) ? if possible, could it be two different colors or just one? //xgm.7c7.myftpupload.com