I'd say it's preeeetty important to tell whether or not the TNT block you're about to break will safely drop as an item and no longer be a threat, or do the opposite and start detonating when broken... Yep, unstable TNT still exists in vanilla, and certain maps or servers make use of them. This pack makes them a deep blue, so that they are - rather prominently - marked as unstable.
This paragraph used to be a note about Faithful's relation to this pack. Unfortunately, I am withdrawing my support for Vizzy's Faithful. More context here.