Colors assigned to emails for sorting are disappearing

i don't use outlook, i have been using the comcast email interface and just manage them on the web.  I have had this account for 10 years with no issues, i have been assigning colors to important emails to keep them at the top.  About 3 months ago, all the colors vanished...i had to go hunting for the emails and it was very time consuming.  I got my colors reassigned and this morning all colors gone again.  What is causing this, I rely on my system to work and something is causing the colors to drop that is not me.   I have found some older messages that still have the color attached but are not included in the color sort.