this image has two groups:

at first glance did you separate it into red v blue or circles vs squares?

you're absolutely making things up. we've evolved to differentiate shades as well, which supercedes colors. even for colorblind people this kind of image should be differentiated by color or shade first.

not to mention not all people have perfect vision, in fact people with blurry vision probably outnumber colorblind people, and that would make the shapes not extremely reliable, especially when most icons would be more or less squares and circles with small details changed.