[JLA]

We have been doing a practical with the electrolysis of 0.5 mol L^-1 KI(aq).  The solution we started out with was a pale yellow colour, though some groups seemed to have a darker yellow colour and some were so light they looked clear.  I thought the halides were colourless in water?  According to our data sheet, they are not listed as one of the coloured ions.  Also, why the variability? 

[Borek]

If it was yellow, it probably contained some free iodine.