Building Term Facet For JSON object

Hi All ,

Hope you are all doing well . 

I have been facing an issue to build a Term facet . 

My JSON object in FIND index will be like below

"FilterAttributes": {"thredcount": "100","colour": "blue","Size": "small"
    }

I am using the below code to build the Term Facet

 .TermsFacetFor(x=>x.FilterAttributes.Root.Values(),x=>x["colour"].ToString(),x=>x.Name="colour")

unfortunately its not working as I expected .  Term Facet count always zero.

Expected result : 

blue (1)

Request you all to let m eknow what worng woth my code.

CMS Version 11

Commerce Version 11

Find version 13

Regards

Venkata Phani kumar R