We use color-coded tags and fields. They are quite useful in communicating to the user what type and status of work awaits him or her.
The logic of color of tags and fields in calendar view has evolved. Presently, if you have tags and fields that have color designations, the color that appears in calendar view is based on chronological order. Therefore the only way to change it is if you remove and replace your metadata. We use fields as a status indicator so we change them frequently. Therefore, the colors we expect are often confusing because the chronological ordering makes the unchanged tags/fields appear in calendar view.
The bottom line is that it would be helpful to assign that a field is always the color that appears in calendar view regardless of what other metadata is attached to a task/project. This uniformity would go a long way.
Happy to clarify if necessary.