Unfortunately the functionality that you are looking for is not implemented. I have created a feature request on our feedback portal - here
, and I encourage you to vote for it.
Regarding the CustomFieldReferences tag - it is deprecated and is not used any more. There is already a bug in our system for removing it from the advanced settings of existing projects.
And about the FieldColorMappings they can be used only for the pre-defined properties in the advanced settings and are not applicable for the custom fields.
If you have more questions do not hesitate to contact us again.