I've searched through the posts and I've been through the (many ) options for the theme but I can't find where to change this background colour.

I've found where to change the rest of the background colours but this one has me stumped.

I would like the date line and the background of the add this image to be the same as the rest of the background.

Thanks for your help,
Karen

See Style Posts/Pages -> Footer Box...

For the Share This Image, either look up the ID or class of that image and add a CSS Insert

img.class-name-of-share-this {
background: transparent;
}

Or style all images in posts here:

Style IMAGES -> Images in Posts

Thanks - it's so easy when you know where to look