Although they may work with other dyes the following hints are for the Semi Permanent Hair Dyes sold on Beeunique.
(these dye removal / fading tips may not work for everyone)
Shampoo hair as often as possible - dandruff control, dish soap and clarifying shampoos generally cause colour to fade faster, Clarifying shampoos are particularly good as they remove any build up of styling products etc on the hair that might be stopping the colour from washing out. Using these too often can dry out your hair so remember to condition well afterwards.
Direct sunlight can significantly fade your hair dye colour making it an easier/lighter colour to dye over
Rinsing hair in hot water after shampooing opens hair cuticles and can allow colour to fade faster (use as hot as your can bear without scalding yourself).
A soap cap is diluted bleach - 1 part bleach powder + 1 part developer + 2 parts shampoo. This can damage your hair as it contains bleach so be careful and check regularly, however it should be less harmful to your hair than full bleach. More info on Soapcaps can be found here
A colour stripper does not bleach your hair but it should remove any colour that is on your hair and bring your hair close to its natural colour. Development time could range from 20 minutes to over an hour depending on your hairs dyed colour and condition - always follow the manufacturers instructions for use. Note: Colour Strippers are mainly designed for use on permanent dyes so results can vary when used on semi-perm hair dyes however some removal of the colour should be visible when using these.