from brown to black

To look good in black, you've got to either be a winter, an autumn or a spring can pull it off with dark make-up. If your light skin is very pale and cool toned (no yellow), you might be a winter.  Do you look best in black, white, light lavender or silver?  If so, you might be a winter, and very blue black would look good on you (may look a little gothy, but I always loved that look on winters).  From what you say, you probably aren't an autumn (though without seeing a person it would be hard to say for sure).  If you look better in warmer colors (yellow and peach) you might want to consider going for a black that is really a very dark dark brown that looks black and has more warm red undertones in it than blackest blue black does. 

Be sure to either remove the iron from your hair before you get it dyed, or do a test strand to make sure the iron isn't going to do anything not-so-funny with the dye.  You can buy products to remove the iron from well water hair...Malibu 2000 is one.