Paul,
I agree with Steve on this one - especially with 'synthetic ' blackcurrant stains.
Whilst the product sugested by Ken works well, the RX Juice and Dye remover ( also formulated with sodium metabisulphite ) contains additional ingredients that give it the edge.
Interestingly I find agitation has little effect - dwell time being more important. For realy difficult stains, the thermal transfer method does enhance the effect.
John.