Dye run is a fairly common problem for all kinds of rugs and is often due to the red colour bleeding into the paler areas on the rug. Any type of rug can be affected with dye run but it is more common with those rugs dyed with natural or vegetable dyes. Synthetic dyed rugs are much more resistant to color run than vegetable or aniline dyes.
Dye run usually happens early in a rug’s life. Most rugs are washed to remove excess dye in the wool as soon as the weaving is finished, and it is then that one color (usually red, sometimes black, rarely blue or pastel shades) will bleed. Rug dyes do not run in an acidic solution but if the washing water is alkaline it can lead to instability of the dyes and bleeding of colours Add a little vinegar to the water if you are washing your rug to make the water acidic and lessen the risk of dye run .
Unfortunately if one or several colour bleed in the first wash, those colours then stabilise and the dye run becomes permanent. Colour run in rugs is very difficult to remove. One solution is to strip out or bleach the affected colours ( usually white or cream or ivory) this is an extreme remedy and can affect the strength and appearance of the wool fibres. Eg if you use a caustic colour remover it spoils the sheath of the wool fibres and alters its texture and lustre.
Avoid buying a rug with even a hint of colour bleed. Examine the margins of the coloured areas and don’t buy those rugs with any blurry outlines. An existing problem will only get worse. The exception is when you feel that even if colour run exists there are other qualities in the rug that balance the disadvantage of colour run . If for example the colour run is very minimal or is not very obvious then again an exception may be made If you have to look closely to find color run, ignore it as unimportant.