A suspension instead of a solution?
You mix by shaking, and after some time, the powder settles, leaving the liquid alone. It works with graphite powder, tungsten carbide powder, and so on.
You can adjust the settlement time by the powder's fineness and the liquid's viscosity. Indian ink takes years to settle partially.
Graphite is black, tungsten carbide deep grey, many oxides (TiO2...) are white and some are nicely coloured. The liquid can be a colourful solution as well, by a metal ion or an organic dye.
Graphite, tungsten carbide and titanium dioxide are easily available as nanopowder, so you can begin experimenting with these.