A common question users often ask for is to change the color of AX forms when logged in to a different company. This comes from may legacy systems having this behavior. It turns out changing the background color on AX form results in a pretty ugly experience due to the many different layouts of form, group and subgroups, and other controls that would all have to have their backgrounds changed.
However one interesting way I found to provide similar behavior to this is to add a color bar across the top of forms similar to the workflow status bar indicating the company logged in to.