@jefferis Ah okay. I’ve just had a look at how you are trying to do it. My understanding of it is that they (Properties > Background color) are predefined styles within Bootstrap Blocks and if you want a color outside of the predefined set then you would have to do it the way I mentioned above but with one slight change. I believe it would be considered best practice, to prevent your new styles being overwritten should there be an update to the Bootstrap Blocks css, to add any new styles to the custom.css file. Hope this helps.
I’ve just gone back through this thread and re-read your reply to me re: context and I understand what you meant now. Sorry my bad for not getting this earlier!