I've borrowed a book "The Complete Book of Decorative Paint Techniques" by Annie Sloan & Kate Gwynn because I want to limewash some of my walls too. You will get all the information you need about colour mixes. Interestingly, the book says you can probably achieve the same finish by using diluted emulsion paint over an emulsion basecoat - so long as you're not a die-hard purist! A revised edition of this book is currently available on Amazon.
For a bright blue you can use the old-fashioned 'blue bag' whitener that you find in very old-fashioned hardware stores. It was traditionally used on pantry ceilings, as blue is meant to deter flies.
Sheep raddle powder works reasonably well, too, if you live in a rural area and have access to a local farmer's co-op or agrimerchant. You can get it in blue, red, green, yellow and black.
I used some of their Ultra Blue recently. I mixed it with white linseed oil paint to paint a new balustrade on our beach hut. Thought a few feet from the North Sea, salt spray and sand blasting, would be a good paint testing environment
Blood was once a popular pigment, thats what suffolk pink is. So if you have an unexpected murder on the premises you can at least make the most of it.