There has been previous work that was similar to what I think you mean (and predates AprilTags) [1]. The idea is to use markers that are grids, with each cell colored either red, green or blue; tag detection is then done by finding the rectangular region of the image over which the average of the RGB contrast function [2] is maximised. Thus tags are detected based on color without having to do edge detection across the whole image.

[1]: http://www.alexwg.org/publications/ProcSPIE_6623-662304.pdf

[2]: at a single pixel, this is sqrt((r-g)^2 + (g-b)^2 + (r-b)^2))