True and false, assuming color has one tech cofounder. What they need at this point is an Android and IOS client that can take pictures and record the current position of the user then you need a backend system that can handle the massive concurrent upload of pictures and do concurrent geo-spacial lookups. This is by far the most difficult part but MongoDB has a filesystem component and there is a plugin for Nginx that allows you to serve files directly from it.

The geospacial indexing can be accomplished by creating a 2-dimentional index of picture buckets where each bucket contains the pictures taken within a small geographical area (say 2000x2000 meters) then all you only have to iterate over the pictures in the buckets that are within the current distance from your location. The clients can easily sort their images before their are uploaded.

It may sound complicated but games do that kind of thing all the time, and often with bigger constraints (skipping a picture or two isn't going to be a big deal).

So yeah devs are not cheap, but a technical co-founder should be able to develop this.

but could you make Color.com in a weekend?

The android client capable of taking pictures and communicating with the service? Yes (minus the graphics, I draw like a retarded goat).

The service behind? No, but I highly doubt they have been spending only a weekend on it.

In two months? Properly, though it assumes that there is nothing more to it than has been described so far.