
Clearly we are not as advanced painters as most here, we just use colours out of the pot (thinned of course) but no mixing for any large batches of colours, uniforms, walls etc.
The only mixing we do is on things like flesh and power/magical swords then its more blending.
These things are such that is not at all vital that the mix ratio of the colours is the same, in fact with flesh it is better that there are some differences.
Given that we paint armies we started using established paint schemes so we just follow online instructions so its easy to reproduce the paint job for any units you add later.
We have a more bespoke paintjob on our Necrons but again there is no mixing but we have a word doc recording what colours are used for what features. It can be vital to get the correct basecoat colour to glaze over to achieve a constant effect across the entire army.