Mixing paint by weight is fast, precise and easy but you need to get a good milligram precision scale.

You can't use cheep scales since they are far too slow.

I can recommend scales from Sartorius. They are fast and made to be used in the same way a painter are adjusting paint mixes

Using a scale for mixing paint is normally not useful but if you are using the PaintMaker color mix calculator it can be a good and fast way to achieve precise paint mixes in the right amount. It also has the advantage that it is possible to mix the exact same color again. And you can work in all light conditions and still know what you are doing.