Color-deposit shampoo for very dark hair

[#1]

  I have naturally dark brown hair that is professionally colored black with traces of dark red and violet mixed in. 

What is the best color-deposit shampoo (and conditioner) to keep my color rich and dark ?

[#2]

The product I use is Artec Color Depositing Shampoos/Conditioners. They make a variety of shampoos/conditioners for different hair colors/shades/tones etc. I have red hair (I get it professionally colored) and I use one of their red shampoos and it puts back color to my hair and makes it not as brassy, dull, washed out and it just keeps it rich looking. 

Here is a website:

haircareusa.com/artec_color_depositing_shampoo.htm 

Hope this helps!