I spent last night looking at various Youtube videos of people using Tru-Oil on guitars and came away with the impression that most were unaware of the basic chemistry of what they were doing.  But I must admit that I was so excited with the prospect that I had difficulty sleeping.

Tru-Oil is a partially linked polymer that extends the links when activated by oxygen.  Once the bottle is opened, it starts to "turn" like a bitten into apple.  So the trick is to keep it from oxygen until it is actually applied to the wood.

Second, the main ingredient of Tru-Oil is also the carrier used in oil based artist paints. So I should be able to find a color fast pigment mix among the oil based artist paints that I can add to Tru-Oil.

My first thought was to mix the Tru-Oil and artist pigments into a reusable aluminum aerosol bottle with some glass marbles, seal it, pressurize the can with argon, invert the can and release some of the argon with intrained air, and refill with argon.  This should be close to an oxygen free environment which will keep the Tru-Oil from degrading.

I would apply the Tru-Oil from the aerosol can (after shaking it to mix it with the oil pigments) on a paper coffee filter covering some cotton balls, working small areas at a time.  The violin would be hanging on a string from the ceiling with the fingerboard masked off with  painters tape.  

I know all plans change after the first punch is thrown, but the above are my first thoughts.