I see green lights as white, which is fine most of the time because of the order.
The exception is when there's a lot of glare from the sun setting behind me, and I sometimes can't tell if it's green, or just the sun reflecting at the right angle. It also washes out the red and yellow, making it harder to see if they're lit.
I am the same--green traffic lights are nearly white. Normally, it's enough to know it's not the red or yellow light. Sometimes at night--face with an array of white lights in the distance--it can be an issue.
At my last eye test at the RMV, the clerk tried to tell me I wasn't color blind. I mean, sure, I've been able to drive with it for 40 years, but I know damn well I'm color blind.
Funny thing, I'm NOT colorblind and apparently I only rely on the color. I've been driving for over 10 years now, mostly in the capital that has traffic lights everywhere, and sitting at my desk now not looking at a traffic light, I wouldn't want to bet money on the order.
Yes. They can still drive fine, but don't get the benefits of color coding, like being able to infer whether red or green is lit from the light reflected off of other objects. That becomes somewhat important in low visibility situations where the position is hard to determine.
I just happen to have a friend with red-green blindness, who was my reference point in answering. It's good to point out there are different types with different impacts, though.
With the switch from incandescent bulbs to LED traffic lights it would be very easy to change the shape of the lights: e.g. octagonal for stop, triangular for caution, and circular for go. Keep the colors, but add shape as well. Seems like an obvious and useful change to me.
If they're roughly the same size and in the same order as the round lights today, people with poor visual acuity would still see more or less what they see currently.
Horizontal lights are not consistent across countries. The linked article has an image of a Japanese horizontal traffic light with red on the right, whereas an American traffic light would have red on the left.
Which is even worse. I grew up in an area with only vertical lights. After several years of driving I ended up in an area with a horizontal light, one end was white and I had no clue if that meant stop or go. (I'm colorblind so I normally think top=stop, bottom=go)
AFAIK yellow + green is only ever used for turning traffic and is always installed together with a regular 3-bulb traffic light for the other directions. Stand-alone two-bulb traffic lights are always red + yellow, with red on top, just as usual.
Almost fifty years ago, I worked with a guy who was color-blind. This was in Colorado, where at the time some of the little towns in the mountains still had traffic lights arranged horizontally rather than vertically. He must have known the order at one time--I think I learned it for my license test--but of course with little chance for reinforcement tended to forget. I suppose that such lights are all gone now.
That argument has two issues: First, not all US traffic lights have order, as single-light ones replace stop signs in some (mostly suburban/rural) areas. Second, light position is still hard to discern at night.
My personal take: the red and yellow hues in traffic lights are often indistinguishable for those of us with red-green colorblindness.
Also lights with more than three bulbs, some indicating left or right turns, of which will take on two or more colours themselves. Some lights have a bulb above red for cyclists and transit. Some lights called beacons are a single bulb that take on several colours.
I see green lights as white, which is fine most of the time because of the order.
The exception is when there's a lot of glare from the sun setting behind me, and I sometimes can't tell if it's green, or just the sun reflecting at the right angle. It also washes out the red and yellow, making it harder to see if they're lit.