A simple card categorisation mechanism that allows a Recall user to:

(i) Determine and set the categorisation, e.g. based priority/level of importance, work status (to read/read/to share all based on colours (just like categorising email, calendar events etc in Outlook, Thunderbird etc

(ii) The colour should tint the card's icon in the sidebar which will be a quick visual clue when viewing the Recall sidebar/tags

(iii) The colour codes can be filtered

(iv) The colour codes will show up i the graph view, though this needs to be figured out with the existing palette in graph view.