Some checks for loading related layers are insufficient to deal with the case where multiple observations are loaded at once - for certain types of load the fact a layer is loaded is not recorded along with the observation name, so the layer will only be loaded for one of the multiple observations.
Error occurs in loadRequestedChildren and loadRequestedParent only.

Fixed loadRequestedChildren and loadRequestedParents to check for colour not layer of requested elements. Ran test suites and they pass.