A very interesting observation, MC

For the general reader: here is a very brief, but effective description **LINK**

https://www.testingcolorvision.com/tcv-anomalous-trichromacy.php

I well-remember a colleague who had difficulty with a ‘project management’ chart, on which we used two colours of adhesive tape … ‘Kawasaki Green’ and ‘Orange’ … He simply could not distinguish between them.

MichaelG.

Hi, I don't have any colour problems, but I also found the graph difficult, although I got it correct according to JasonB's example. It is the top, the second and the fourth lines down that are hard to tell which is which, with the second and fourth being the most confusing, but I concluded which ones were which by the speed range and the materials, which of course can be difficult to those who don't have a clue. It may have been better to have put A B C D and E adjacent to the ends of each line on the right hand side.

Regards Nick.

As Nick says a complete beginner would have difficulty arranging those materials DC31K. Just look at the Proxxon saw thread no idea of what speeds are needed or why and did not know how to work out rpm given the cutting speed of the material.

I have sympathy with ‘colour-challenged’ individuals. I am red-green deficient.

Anything I call faintly pink is bright and obvious to most (I describe many apparently pink items as plain white) – I have clothes with thin stripes of colours that I have no idea of their presence, which makes dressing in matched colours a joke (my wife is very colour conscious).

Just one more reason for leaving a job was that adjacent spectral colours were used to indicate process-control parameters, as they deviated from target. That meant I could not recognise that the process was in need of adjustment until the lights started flashing! Far too late for easily maintaining a steady state. That happened to be just one fault, of many, with that particular installation.

I was the ‘dummy’ for demonstrating the colour blindness check-pictures for one lecturer at college – at least it gave the students a good laugh (and possibly uncovered one or two students who were similarly afflicted, but didn’t like to be seen as disagreeing with the majority).

One job I had required results to be written down as a record (yes, back over half a century ago!). When the fellow, whose regular job it was, went on holiday I covered for him. The number of times I used a red or black pen instead of the correct one was overly common – until I labelled the pens appropriately.

It was a good thing that I never wanted to become a train driver!

.

Your point is well made, John … and I suppuse the short answer is NO

The site that I linked last night has some excellent illustrations.

The classic way to avoid this problem is to use shape as distinguishing feature.

e.g. Lines can carry markers [squares, triangles, etc.] to distinguish them … either instead-of, or in addition-to, the colours.

The use of colour alone is, I suggest, a triumph of style over function.

MichaelG.

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Edit: __ This is the best example I can find of a toolset:

https://www.wavemetrics.com/products/igorpro/creatinggraphs/2dgraphs/linegraphs/graphmodes

Edited By Michael Gilligan on 27/04/2021 09:47:25

Though when I was 25, Jason's version would have been printed in Fifty Shades of Grey, even worse!

Seriously though,my experience managing websites suggests it's impossible to select colours suitable for all possible vision issues. There are many special needs, and adapting to one is likely to make the others worse. Catering for average sight and avoiding colour blind combinations annoys the fewest.

Many practical difficulties too. How does a person with perfect colour response conceive what the world looks like to those with various degrees of colour blindness? Not even sufferers are always aware they have a problem: a teenage friend only discovered he was mildly colour blind when the class looked at a selection of test cards during a biology lesson. He'd passed the medical!

Another difficulty is imagining how colour will be rendered on different media – paper and computer screens are completely different. Only certain colours are 'web safe', and they don't necessarily work well on paper.. I often use QCAD to draw examples on the forum: on screen QCAD draws on a black background, but printing inverts to a white background. Certain combinations like Yellow on Black are wonderful on a light emitting screen, but poor printed on paper and useless when converted to yellow on white on screen. As is printing yellow on yellow paper.

Avoiding colour clash problems is partly skill and knowing about eye conditions, partly aesthetic because people with normal colour sense find certain combinations obnoxious, and partly technical involving expensive colour calibration techniques and expert review. Graphs are extra difficult because the palette of clearly separated line colours is small – subtle shades of colour don't work. Marking points with different symbols like circles, crosses, triangles etc might help, but their numbers are also limited. Worst of all they tend to clutter the graph making it harder to understand, which triggers even more complaints.

Engineering is all about compromise and nothing is ever perfect…

Dave

Frances,

That does seem an excellent solution, for a simple graph where the traces don’t cross

MichaelG.