As you say, if you pack comfrey leaves into drainpipe and let it drip, you get very dark brown liquid. If you add water, you get a lighter colour. It all stinks to high heaven however you make it I'm afraid
I don't think you are doing anything wrong, you have just made a dilute mix you can dip a can into and water with. After 3 months of steeping, all the good stuff will be there in the water, so you have got what you wanted