How to symbolize a large amount of points with lots of color

Question

I have an interactive map with a very large amount of different points. Depending on user selection, various points are shown or not-shown.

These points are divided into several categories, each with potentially 20-30 sub-categories.

My current idea is to create a general hierarchy like the following:

Cat 1 => blues
Cat 2 => greens
Cat 3 => reds
Cat 4 => browns

Each of these color groups would be divided into colors based on some criteria in each category.

I'm not concerned with color blindness issues (too many colors needed to worry about this - plus, there is a popup attached to each point giving far more detail). I'm not even really concerned too much with differentiation beyond the 4 categories, but I did think it might look better if there was some differentiation.

I've looked at Colorbrewer, but they don't have recommendations for this amount of colors.

So my question is what you all do for color symbology in situations like this? What are (if any) best practices when you have to deal with a lot of different colors?

Answer 1

When you have that many colors (80 to 120 if I understand correctly), you simply can't have a clear representation, as color gradients are not easily differenciable. I'd recommend using different symbology, (not only dots) to limit the amount of colors needed, then try to work out easily distinguishable colors for each symbol, allowing you to reuse them.

e.g : 4 symbols for the categories and 20 to 30 colors for each sub-category (which is more manageable in terms of color finding).