But what of those weird yellow stop signs, you ask?
The AC/DC-powered unit runs on 5-36 VDC SELV or 90-250 VAC with a low input burden that keeps voltage drop to less than 1.5 V for full-scale current and support wide 0 to 1000 ohm load range with no trimming is required if the load varies. The splitters are DIN-rail mountable and feature removable terminal blocks.
Red symbolizes danger in many cultures, which makes sense, considering it has the longest wavelength of any color on the visible spectrum, meaning you can see it from a greater distance than other colors.
With the ironic exception of stop signs (not stop , just signs -- more on that in a second), red has meant stop since long before cars existed, with train signals' use of red dating back to the days when mechanical arms lifted and lowered to indicate whether the rail ahead was clear. Green's role in lights has actually changed dramatically over time.
Its wavelength is next to (and shorter than) yellow's on the visible spectrum, meaning it's still easier to see than any color other than red and yellow.
Back in the early days of railway lights, green originally meant "caution," while the "all-clear" light was, well, clear or white.