Here's what was common then:
* No polish: Women typically went bare-nails. This was the standard before the invention of modern nail polish.
* Tinted cream: Some women used a very pale, tinted cream to give their nails a subtle hint of color. These creams weren't very durable and would chip easily.
* Red dye: A few women might have experimented with using red dye on their nails, but this was uncommon and messy.
It wasn't until the 1920s that the first true nail polishes started to emerge, and these were typically in dark shades of red, maroon, or black.
So, if you're looking for a historically accurate color for a 1912 costume, you might stick with a natural or very pale pink shade, or simply leave the nails bare!