Many dented fenders later, the first signal indicators show up. This article makes clear that both the break light and the turning signal indicator are both the same color (red) but they are an improvement on what was sporadically used in a few circles: the "Illuminated Glove" (a fingerless mit intended for the left-hand that was supposedly easier to see when making stop or turning gestures).
Click here to read more about the cars of the past.