Re: cold generation

For the most part the colour of CS comes down to particle size, shape and density(ppm).
And so with regards to your own observations, it's likely that you didn't run your heat processed batch long enough to reach colour.

That said, on the issue of solution temps and processing it's interesting to note that room-temp solutions can be processed to exhibiting colour in much the same way of the heat processed solutions. With the exception of the saturation potentials between both solutions. ie, the room-temp solution will exhibit a lower saturation point(ppm potential) reflected in stability(dropping out, plating, pooling etc), whereas the heat produced solution will prove to have far higher saturation limits.

Beyond this, there are of course numerous other advantages in processing CS using heat also:
1. Raising the initial conductivity of ones solution.
2. Reducing silver ions into elemental nanoparticles.
3. Raising the saturation point and stability of a solution.
4. Increasing the overall resistance to oxidation.
5. Gaining the ability to decrease particle size and solution quality

Hope this helps.

PS. Often times, current works out to be far more important than voltage when making CS