I've recently re-stuccoed my house. Ive decided that instead of painting it, I would rather do a limewash. I've mixed several batches with different proportions of mineral pigments trying to get the right color. My problem is, I got a mix that is about the right color and did a test area on the stucco. It looked good except once it dried it was alot lighter than what I wanted, which I expected it would be. Later I sprayed it with a mist of water and suddenly it was the desired color again. My question is how do I retain the 'wet look' without using a sealer or such.

you cant,

this is one of specific characteristics of lime paint.

You can seal it with "breathable sealer" though - you can get it from adicolor.com

or make your own because it is virtually a casein mixed with a little bit of lime, resulting in casein glue (lime is one of the chemicals that turns casein into glue).

This is how the historic distemper was made

andrea mantegna used this technique (distemper) a lot
http://truefresco.org/bookshop/4_1000_Mantegna_sr_1_Books.html