The Alkali shampoo will remove any 'over-deposit' of color as it will naturally strip excess color from the hair. The 'acid' balanced conditioner will remove any residual alkali from the hair shaft and naturally balance the hair back to its original acid balance. Skin, hair and nails are acid balanced due to the amino acids that make up our bodies molecular structure. Alkali is drying to the hair, but is necessary to remove excess coloration from chemical color processing.
Read the label on the bottles of shampoo and it should tell you if they are acid or alkali. Generally speaking, most 'regular' shampoo's are alkali based. Most conditioners for dry hair are acid based, so you would probably do just as well with your 'regular' shampoo if you use a good moisturizing conditioner after coloring.
[This message has been edited by Marti (edited 07-14-2003).]