The two photos I posted were a set of clear-lens GE RX11s on top (a shameless Flickr grab) and the bottom shows a previous generation of tinted-lens Dialights shot by yours truly here in Portland. The Triana Boulevard and Memorial Parkway pictures both have tinted red lens LEDs, incandescent yellows and since the greens are on, I can't tell but I'd assume they're clear. Your last photo has a tinted yellow ball (I think) and a clear green arrow.
The average person probably couldn't tell the difference between a tinted lens LED and an incandescent lens if you put a gun to their head so there is an art to identifying the difference and that's learned through glorious nerdy practice. Basically if you can tell what color the LEDs are with the light off, the lenses are tinted. If they appear silvery-gray and you can't tell what color they should be when off, the lens is clear and this is due to the fact that the individual diodes themselves are not colored but instead, glow a particular color when energized so the tinted lens is more decorative than anything else. They certainly aren't necessary. LED units can be easily identified over incandescent signals by their 'snap' instant on (better seen at night) and differing green color whereas incandescent bulbs fade out relatively gradually and the green is not quite as blue.