Im facing same problem at moment, i used to use Score which seems to be the lightest colour leadcore around but it still gets darker when wet (and old n dirty). I played around with using 25lb IQ but wasnt convinced.
Im currently using 1.2mm clear shrink tube in lengths from 20"-48" shrunk down onto the mainline AND a length of lead (similar to that used in leadcore, but bought from flytieing section of tackle store, vcheaply), rigmarole sell 1m lengths of the shrink down tubing for £2.70ish but ive just bought 10m(!!) from ambaits.co.uk for £4.99.
Its still early days and im colouring it with TFG pens but it sinks quickly and is certainly less obtrusive than leadcore..
Hope that makes sense??