Has anyone tried Directions Pre-colour shampoo to strip out SFX?

I've used this and to be honest it did not remove the colour much at all. Good for giving a good clean base for dyeing with no big product buildup though.  I personally would stick to the trusted methods of using a clarifying shampoo, washing hair more often using hot (not scalding) water and if needs be a soap cap/bleach bath.

Will your new colour not work over your current one with a little fading?
What colours are you thinking about?

I'm swaying towards deep purple (SFX) at the moment.  I know that eventually I'll go back to black because the semis are a pain to keep up and bleed/stain everything, so as my hair grows longer it'll only get worse!
In the meantime, I'm thinking of going deep purple for the next few months at least.  It'll probably work over a faded base, without too much colour removal needed (I'll need to bleach bath my roots anyway), but I want to remove as much as the dye as possible so that the purple has optimum chance of actually sinking into the hair.  Same principle as putting your semi dye onto dry hair instead of wet - if your hair is wet, there will be water molecules in the hair shaft in the places that you want the dye molecules to go into, so less uptake of dye on wet hair than dry.  Likewise, if I can remove as much of the red dye as possible, then the purple will have more spaces in the hair shaft to go into as they won't be clogged with red dye!
Of course, I haven't made up my mind yet, and I might decide to just be boring and go straight to black, then buy some human hair extensions and dye them purple to add a flash of colour as/when wanted!