Your variable is “colArray”, but in the loop you’re referring to “colArr”, which either doesn’t exist or is a different variable.
Functions are always called using (), even if there are no parameters. So you need ToString(), not ToString.
However, using ToString() to compare color values is a really bad idea. One, it’s a lot slower than just comparing color values directly. Two, the formatting is not guaranteed to stay the same, so while it might work in one version of Unity, it might stop working in another version. So ditch the ToString() stuff and just compare colors, which will always work for sure and is way faster.
A minor thing, but MapArrayData should be mapArrayData, to be consistent with Unity naming conventions (makes code easier to follow when variables and functions are easily distinguishable). Also you can use mapArrayData += “white”; for shorter code.