In the Thread pane (AKA 'Message List' pane), TB 102 precedes the Subject field with an angled arrow pointed to the left if the message has been Replied-to, and pointed to the right if it has been Forwarded. Those icons are combined into a third icon - with arrows pointing both left and right - when the post in question has been both Replied-to and Forwarded. All this is straightforward icon design: the third icon uses a combination of the first two icons to signify the combination of their respective meanings. The icon colors are just the opposite. The Replied-to icon is purple and the Forwarded icon is blue, so we have 'Replied-to' icon= left-purple, AND 'Forwarded' icon = right-blue. BUT the combined 'Replied-to AND Forwarded' icon = left-blue AND right-purple. So the relationship of direction to color is not consistent, but inverted. Do these cross-attributes have any significance? It was not always so. These attributes used to be applied with consistent, rather than inverted, meanings. A Mozillazine article shows an earlier version. The icons are different (the article vintage is TB 2.0, and much has been tweaked since then), but there the arrow colors and directions are mutually reinforcing {Replied: green-left; Forwarded: purple-right; Replied and forwarded: green-left and purple-right} - so the color and direction attributes coordinate to reinforce the functional significance. How can I find the release notes covering the change in these icons, to see what significance is intended?