Indigo Blue - I actually bought an indigo starter kit last year, and still haven't tried it! But I had a request to dye something in an indigo blue shade last year, so I did some experimenting and came up with this recipe:
Indigo Blue – 8 ounces
3 T Cerulean Blue
½ tsp Deep Orange
¼ tsp Lemon Yellow
1st – full strength
2nd – 1 part full strength, 1 part water
3rd - 1 part full strength, 2 parts water
4th – 1 part full strength, 3 parts water
You could take this even lighter by following the ratio changes as described above. I really like this color, and have used it for several shirts.