Question about spreadsheet

I am looking at the spreadsheet of Podcasts and YouTube pages and I noticed that certain ones are highlighted in light blue. Does anyone know what that indicates? Apologies if this is explained somewhere. I tried to look for a key somewhere in the spreadsheet but did not see one.

Edited: it appears that I have the reading comprehension skills of a turnip. It is clearly stated right at the top that these are the resources that get the most recommendations. I need to apologize to my kids for every time I have lectured them about reading directions more carefully.