User blog comment:DaNASCAT/Technical Update: February 27, 2017/@comment-1474707-20170228194225/@comment-1474707-20170228202006

Ahh. I've been noticing WebP quality downgrades for a while. It's most obvious for a set of icon images we have, because often (randomly as you reload the page) some of the images are displayed using WebP and some are not, so you end up with different colours (note the 4 is a brighter yellow than the WebP'd others)

https://s16.postimg.org/4p2bgiofp/imrep.jpg