I read that to make the colour navy you have to mix black and royal blue. Well, I had ready made mmf of both of those colours and I mixed them but have come up with a sort of dark grey/ purple. Does anyone know how I can make it into navy or can it not be redeemed and I should start over? & if so how much of both these colours should I add?

I have a gel color from Sugarflair called Navy Blue. This doesn't help you now but I would just keep adding black to get the right shade of Navy Blue.

I would actually add back more royal blue. Black food coloring tends to have purple and green hues to it. I just made some navy and started with MMF colored with royal blue (Americolor). Then I added in a few drops of black Americolor to start the darkening process, but I also noticed mine was a bit purplish/slate gray, so I added more royal back in. After it was looking a little more blue, I rolled in a small amount of premade black fondant (Duff's). I ended up with just the right color. But it's possible you may have to start over.

Thanks! I will try to add some more royal blue and see what happens. Here's hoping.......

I have Ameri-color gel in Navy Blue. I did have to keep adding black to it to get it dark enough. Let it sit overnight to let deep colors develop. It worked great for fondant but I also did a logo out of gum paste that was supposed to be Navy, but gum paste dries lighter. So I got my navy blue gel paste and a little vodka and painted it on the navy gum paste and it was the perfect color. It's the Dallas Maverick's cake in my photos.

It's fantastic carmijok.
I don't have Ameri-color bc we can't get them here and they won't ship stuff like that over seas. I use Wiltons which I know will darken so I think I'll wait until the morrow to see what it looks like.

Thanks...but hey...use the Wilton color like I did the Americolor if it doesn't darken enough! Paint it straight on with a little vodka to spread easier. It takes a little longer to dry but it eventually does. good luck!

Thanks to all for the advice, I added some more royal blue and got a beautiful indigo, am thrilled!