oakwood shampoo for greys works very well on my coloured! gets him sparkling! best to buy from places such as burgley as can be expensive on the internet.
for quick fix i use a grooming block to get stains off then brush over with a dandy brush, not brilliant white but will do for hacking. I have heard that putting a few squirts of purple spray in a bucket of water and soaking the tail brings it up gleaming white, but im not sure about that one as we all know how purple spray stains everything. Has anyone else heard of that one?