Is it possible to set a defaultValue when using customFields?
By just using "default": "something" in schema.json atleast in my test with the color-picker-customField this was not working.
That is quite a bummer. 
The only option I see is using: allLayoutData and fiddle me through the data to get the "default"-value in the fieldSchema. This seems very complicated to me?
Update:
I correct myself: attribute.default is what I was looking for. 