Pekka, for layout you want a fast-drying thin-build hard solvent-removable color.
Oil colors are slow drying and undergo chemical change to harden. They are not solvent removable once cured, They tend to flake when scratched, rather than leave a thin line. Acrylics are faster but also also not solvent removable, and very elastic, so hard to scratch in a clean line. Both are high build. Neither is a good choice for layout work.
Usually real layout colors are dissolved by alcohol or stronger solvents like acetone. They flash dry as the solvent evaporates. They often use dye colors, not opaque pigments to keep the build low. They scratch with clean lines. If you are going to try to make your own from pigments and common ingredients, you might consider shellac with a lot of thinner (denatured alcohol/meths) as a starting point for a vehicle. And a dye pigment would be better than opaques, since they are finer.
But markers are so much easier and available, I'd say if it isn't just a matter of curiosity, just use markers. Markers and layout colors are very similar -- fast dry solvent based dyes.
I can understand the internet confusion -- it relates to the difference between layout and spotting. Spotting colors used for hand scraping are not supposed to dry, but to transfer marks from one surface to another. Therefore they are oil based -- and non-drying oils at that. So the two kinds of "blue" (layout blue and spot blue) are completely different in composition and purposes.