Or "color" if you prefer. I was browsing the green_body tag, and noticed a number of tags of bodies that appear to be yellow and sometimes blue to me that have been tagged as green. Some of these could be subjective. It is also worth noting that seeing colour is meaningfully influenced by spoken language.

I feel a little weird about leaving a comment on every picture that I think isn't green, because there are a significant number of images. Should I leave a bunch of comments, just change the tags, or accept that they don't look green but are tagged as green?

You could report the "offending" posts and ask for a color decision, but a better option is to hop in our Discord and ask in #e621-helpdesk.

If you have colourblindness, or believe that you do, you probably shouldn't be touching colour tags. I'd honestly get that looked at first if you believe it to be the case. If it turns out you aren't colourblind, feel free to change the colour tags that don't match because they'd then be clearly incorrect.
In the case of "debatable" colours, such as turquoises that are unclear on if they are green or blue, if you really want to be pedantic use a colour dropper tool and see what seems more prevalent, otherwise, you might want to change your viewing angle or monitor brightness to see if it makes it seem more readily apparent that it's more towards one colour or the other.
Failing that, a "blue-green_body" or "turquoise/cyan_body" tage would also work.

votp said:
if you really want to be pedantic use a colour dropper tool and see what seems more prevalent

Using a color dropper is a bit sketchy, since color is affected by lighting. If the picture's light source or things reflecting light within the picture are yellow-ish, the color dropper is going to say everything in the picture is extra yellow-y. If you Google Image search "strawberry illusion", you'll see some strawberries that a color dropper would think are gray, but a human would think are red.

I've actually seen the issue of colorblindness with color tags happen before so it could very well happen again. Thing is, you'd have to see the individual's tagging habits and see if it's following some kind of pattern. If it's really colorblindness then there would most likely be a noticeable pattern of mistaking X for Y.

Some other issues amount to lighting and adjacent colors as both of them can influence a perceived color more than you might think.

https://www.colorlitelens.com/color-blind-test.html For those interested, found a nice test with explanations at technical level. Had to use 'block element' for the stupid menu bar, though. Laptop LCD screen is only 600 pixels high. XD I remember reading about how antagonistic theory of color was physically less accurate but matched how human color differentiation worked. Namely we don't see how 'blue' something is, but how NOT red and green it is. It's literally subtractive process which is neat from a mathematical POV.

Note: Searched for 'colorblind' 'test' 'image' on Google Images to find this. It's a common test. Other than seeing UV differently, I seem to have full color vision according to every test I've tried. Slight differences in color sensitivity aren't unheard between eyes of the same person. Ugh, cataracts that have gotten worse and worse since I was a teenager, finally removed in 2018 after finally being unable to drive and barely able to read. Oddly, didn't even realize that was what they were, until 2 years before surgary, because they hadn't become occluded enough. I also had a deposit on one knee removed as a child, so probably genetic predisposition to things like calcification(?). I haven't actually checked the UV response since the surgery.

A more medically-accurate 'dropper' test would base it on average of nearby pixels and the overall brightness and hue of the image. It would fit the way human vision actually works. :edit: oops, meant physiologically

https://www.aoa.org/AOA/Images/Patients/Eye%20Conditions/Color_Deficiency_Ishihara_Test_AdobeStock_114210620.jpg Here's a chart. Spoilered to not influence results. I saw:
12 8 6 29 57
5 3 15 74 5
6 57 5 42 45
I noticed that some of them have different numbers hidden behind the 'obvious' color contrasts. From what I remember of taking these tests as a kid, those that see the other numbers have specific differences in perception of color. The blue/violet test (blue circle in the middle of bottom row) was harder to see until zoomed in, but I have problems with _shapes_ at that lack of (grayscale) contrast.

More just to answer the main post's question, despite being a month ago, for most images where green_body is tagged and you think it's blue, it's best just to have both tags.

Colour can be quite subjective, turquoise is in the middle of green/blue and people often disagree on what's yellow and what's orange.

So that people can reliably find the images they're after it's easier to keep both tags as, unless the person tagging actually is colourblind, if one person sees it as a slightly different colour then others probably will as well.

pup said:
More just to answer the main post's question, despite being a month ago, for most images where green_body is tagged and you think it's blue, it's best just to have both tags.

Colour can be quite subjective, turquoise is in the middle of green/blue and people often disagree on what's yellow and what's orange.

So that people can reliably find the images they're after it's easier to keep both tags as, unless the person tagging actually is colourblind, if one person sees it as a slightly different colour then others probably will as well.

Funny enough is the 'green' traffic indicators that are in fact slightly blue, because it actually makes them easier to see for many people. Also, language differences as mentioned earlier. :)

not to forget that this is all digital media and screen setups and build in screen affect colors, too.

https://en.wikipedia.org/wiki/File:Optical_grey_squares_orange_brown.svg

Color doesn't exist, everything is a lie.