Cock-up on the colour front

I mentioned in the previous post that there was a big difference between the colour swatch and the online version of the colour I had chosen. I assumed that the printed version would be the more accurate because viewing colours on a computer monitor is very variable; I was WRONG! The online version was much closer so I've ended up with 5L of a colour I really don't like much. What I wanted was somewhere between Royal Blue and Navy Blue, what I got was rather like Fordson Empire Blue (tractor colour). I am hoping that because what I want is darker, it can be retinted.