Sorry I couldn't look this up earlier, my girls were destroying something downstairs.
That's a website discussing tongue diagnostics. From it:
Blue or purple tongue
A blue tongue is caused by coldness, whilst a purple tongue is caused by failure of blood to move properly - which the Chinese refer to as blood stagnation. It however can also be caused not by a lack of yang but by too much cold. A purple tongue with a bluish tinge is due to coldness causing blood to stagnate, whilst a reddish purple tongue is due to heat causing the blood to stagnate. Where there is excess cold, the tongue has a thick white coat.
I'll be interested to hear what others think about this tongue congestion.
This site has the actual tongue map. The sides on this map correspond to liver and gallbladder. I wonder if you experienced some liver/gallbladder congestion, which might be consistent with detox.
Have you tried adding cayenne pepper to your diet? It's supposed to help a lot with increasing blood flow.
I hope this is helpful (or at least interesting!). There is also a face map:
in case you have breakouts or symptoms on the face, too.