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Comments on How can I improve contrast of red and green, to prove Reverse Triangle Inequality?

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How can I improve contrast of red and green, to prove Reverse Triangle Inequality?

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I need to improve this original diagram to the one beneath, because this diagram reappears on standardized tests with different letters, orientation, position of the vectors. Tests require students to distinguish and label $\color{limegreen}{|\vec{b}| - |\vec{r}|}$ versus $\color{red}{\vec{b} - \vec{r}}$.

But some parents and students gripe that $\color{limegreen}{|\vec{b}| - |\vec{r}|}$ looks too identical, particularly in length, to $\color{red}{\vec{b} - \vec{r}}$. Plainly by eye, my diagram fails to convince them that $\left|\color{limegreen}{|\vec{b}| - |\vec{r}|}\right|$ ≤ $\left|\color{red}{\vec{b} - \vec{r}}\right|$.

How can I improve my diagram? How can I better contrast, or even amplify, the differences (in length) between $\color{limegreen}{|\vec{b}| - |\vec{r}|}$ vs. $\color{red}{\vec{b} - \vec{r}}$ ?

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Red and green is a poor choice for distinction colors (1 comment)
Red and green is a poor choice for distinction colors
Canina‭ wrote about 1 year ago · edited about 1 year ago

You don't say whether the colors are the same in the diagram you show here as in the one presented to your students, but:

Perhaps counterintuitively for many, red and green is a really poor choice for trying to clearly distinguish between two things, especially with no other context.

Red/green color blindness is, as I recall, the most common type of color blindness in people; a fairly significant portion of the population (on the order of several percent) suffer from that condition.

Which means that in a group of, say, 25 students, you can realistically expect that statistically at least one of them will have some degree of difficulty in telling red and green apart.

As a general rule of thumb, and this is also codified e.g. by WCAG (web accessibility), avoid using color as the only differentiator.

Even if that's not the problem in this case, if you are actually using these colors, do consider switching to colorblind-friendly alternatives.