SharePoint column formatting with json for date fields

conditions:

1. if currentField <= now + 10 days, then the cell is colored in red;
2. if currentField <= now + 20 days, the the cell is colored in gold,
3. if(currentfield <= now + 60 days, the cell is green – ( editing lieptas Jul 26 at 11:56)

Woould like the "GOOD" to apply to >60 days and the items @ 60 days to display as a darker golden color - any suggestions based on this:

{ 
    "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json", 
    "elmType": "div", 
    "attributes": { 
        "class": "=if(@currentField <= @now + 864000000,'sp-field-severity--blocked', if(@currentField <= @now + 2592000000, 'sp-field-severity--warning', if(@currentfield <= @now + 5184000000, 'sp-field-severity--good', 'sp-field-severity--good')))" 
    },
    "children": [
        {
            "elmType": "span", 
            "style": { 
                "display": "inline-block", 
                "padding": "0 4px" 
            }, 
            "attributes": { 
                "iconName": "=if(@currentField <= @now + 1814400000,'Error', '')" 
            } 
        }, 
        { 
            "elmType": "span", 
            "txtContent": "@currentField" 
        } 
    ] 
}

I realised I had a logic mistake. The conditions I wanted to fulfil were:

1. if currentField <= now + 7 days, then cell is colored in red;
2. if currentField <= now + 14 days, the cell is colored in gold,
3. ifcurrentfield <= now + 21 days, the cell is green

The following code worked as expected (except, I wasn't able to use HEX color codes and instead used Conditional formatting option titles based on Excel):

    {
  "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
  "elmType": "div",
  "attributes": {
    "class": "=if(@currentField <= @now + 604800000,'sp-field-severity--blocked', if(@currentField <= @now + 1209600000, 'sp-field-severity--warning', if(@currentfield <= @now + 1814400000, 'sp-field-severity--good', 'sp-field-severity--good')))"
  },
  "children": [
    {
      "elmType": "span",
      "style": {
        "display": "inline-block",
        "padding": "0 4px"
      },
      "attributes": {
        "iconName": "=if(@currentField <= @now + 1814400000,'Error', '')"
      }
    },
    {
      "elmType": "span",
      "txtContent": "@currentField"
    }
  ]
}

I can see that you have mistakenly applied these conditions to class instead of applying it to color property of style attribute.

Try below JSON code, it should work for you:

{
    "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
    "elmType": "div",
    "style": {
        "color": "=if(@currentField >= @now + 604800000,'#FF6347', if(@currentField >= @now + 1209600000, '#FFD700', if(@currentfield >= @now + 1814400000, '#32CD32', '')))"
    },
    "children": [{
            "elmType": "span",
            "style": {
                "display": "inline-block",
                "padding": "0 4px"
            },
            "attributes": {
                "iconName": "=if(@currentField >= @now + 1814400000,'Error', '')"
            }
        },
        {
            "elmType": "span",
            "txtContent": "@currentField"
        }
    ]
}