As of today, I can assign card colors based on a number of criteria including work item type, assignee, or arbitrary JQL queries.  However, the color only applies to the left hand edge of the card.

In many cases, I prefer to see a background color across the entire card.    The Ascend Card Colors plugin enables this capability for Jira Server and Data Center, but it does not work the same way for Cloud.    Perhaps there is a missing API or something.

In my opinion this is a capability that should be built in to Jira, as it is in most other Kanban or Scrum tools.   In fact, it would be great if there were a set of 6 or 8 pre-set pastel colors available for use.   You have to use very pale pastels otherwise the color is annoying and overwhelming, and in my experience it takes hours to pick all the perfect colors.   So Atlassian could save us tons of time and aggravation by putting this capability into the tool.

There could be a checkbox:  

___ apply colors to left hand edge of card

___ apply colors to the entire card background

BTW, we know that this capability is possible, because a cards is colorized in yellow if flagged = impediment is set on a card.   All we are suggesting is to generalize this existing capability!