My hair is currently Blue, Green, Black, and Reddish Brown (Roots are Black, Body is Red, Tips are Blue, front is Green)  But I have been looking into Henna (or preferably Indigo) for my hair and I was honestly wondering what in the world would happen to my hair should I try this?  would I end up with some odd colouring with the blue or would it work out fine.  Also  Would Indigo give the same thickness as henna?  What do you think?

Oh my!  I have no idea what henna would do with the coloring you have.  The issue is typically what process was used when you colored your hair.  Certain metals that are used in some coloring products will react with the henna and cause strange reactions.  I would advise you to save you lost hair strands, particularly those that have been colored and do a strand test on them to see if there is any reaction.  High quality henna would also be recommended.  

I'd suggest reading the Henna 101 thread.  It mentions a site that comes highly recommended by henna users.  That site also sells samples, etc., so you can do your testing.  

Good luck!

A strand or harvest test would be your best bet.  If all turns out well with the test,to achieve truly black(indigo) hair,you'd have to use henna first then rinse it out and then do straight indigo.  Visit the henna page to see all the mixes.  You'll learn alot and have a good time reading!!

I went ahead and did the henna with beautiful results except for that large chunk in the front that would not dye.  At least there was no odd colouring after.  I will try again in a few weeks

Glad you got good results!

You use a henna this a best and it looks a very nice,I think you use it and mix a egg,aloe-Vera this a best and it never affect your hair.