How to colour a mathematical expression to communicate the relative importance of its terms?

Question

In a presentation, I have a mathematical expression, say A+B+C, where:

1. A is the main term, both in magnitude and importance;
2. B is a correction term, much smaller than A, but important nonetheless;
3. C is an error term, smaller than the other two and whose faith is that of being neglected most of the times.

In addition, A has been already introduced elsewhere, whereas B and C are new elements.

I want to choose different colours for the three symbols, or sub-expressions, that visually communicate to the audience the relative importance of those terms, as an integration to the speech. The colours should be readable when projected.

I had started with red for A and gray (dimgray of the SVG colors) for B and C, but this does not differentiate between the last two terms.

Then I thought of using black for A and red for C: red would communicate that C is an error, but unfortunately seems to communicate also that C is more important than A, which I don't want.

Do you have any suggestion?

Edit: I removed the example image because I think that at the end it was a bit misleading on the purpose of this question, which is specifically about the choice of colours, rather than the choice of other elements (e.g. size), or on the opportunity of colouring equations.

Answer 1

Colours are really perceptions, and are affected by other surrounding colours. In a colour you can also play with different characteristics, such as hue, saturation, etc, and in your case also with font weight, font size, etc.

My opinion: I assume you will work over white or very light background.

• The best is to use a neutral grey for symbols (+, /, etc)
• Use red for the error (C), but make it less saturated and more greyish to reduce its importance.
• Use black bold font for the most important piece (A)
• Use a dark grey for (B). In my example below, you can make it slightly lighter if you feel it is important to make it more different from A
• I would not use font size to differentiate the terms
• You don't need to use many colours. This is not the annual Indian festival of colours, so keep your colour game elegant.

Example:

(A) #000000
(B) #222222
(C) #d29997
(symbols) #666666

Answer 2

Just by looking at your formula I cannot tell what is important and what is not; perhaps before dealing with different colors your should differentiate levels of importance with different sizes.

(forgive me the potato-quality image)

Regardless of the colors used, it is easier to understand that the bigger elements are more important than the smaller ones. This way you can still use colors to separate blocks in your equation.