JSON to show colors on expired items in list

Question

I want to turn red on items that are expired - to highlight them to staff

 Here is my JSON, it is not highlighting anything.  Expiration is the field name in the record.

{
"schema": "https://developer.microsoft.com/json-schemas/sp/view-formatting.schema.json",
"CurrentRowClass": "=if([$Expiration] <= '@now', 'style: {color:#ff0000'} ) "
}