CONDITIONAL FORMATTING - Unable to format column

Question

I have a SharePoint LIST that's being used to manage events. There are 6 participants for each event and each Participant has a column:

"Participant 1", "Participant 2", "Participant 3", "Participant 4", "Participant 5", "Participant 6"

I need the FILL color of Participant 1-3 to be Green if EMPTY and Transparent if NOT EMPTY I need the FILL color of Participant 4-6 to be YELLOW if EMPTY and Transparent if NOT EMPTY

I have been able to accomplish the above - my issue is that the "[$Evenement]" column has two choices; Orientation/Formation. If the selected choice is Orientation - I need the Participant 4/5 columns to have GREEN fill IF EMPTY and Transparent if NOT EMPTY. Below is the code that's not working for what I need. Any help would be appreciated - I am a complete newbie to JSON.

{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
  "elmType": "div",
  "txtContent": "@currentField",
  "style": {
    "background-color": "=if(@currentField == '', '#98FB98', if(@currentField == 'blocked', '#FF6A6A', if([$Evenement] == 'Orientation', '#FFFF66', '')))"
  }
}

Answer 1

This should work. You just need nest one if() inside the other like so:

{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
  "elmType": "div",
  "txtContent": "@currentField",
  "style": {
    "background-color": "=if([$Evenement] == 'Orientation', if(@currentField == '', 'green', 'transparent'), 'transparent')"
  }
}

Update. Final code version

{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/column-formatting.schema.json",
  "debugMode": true,
  "elmType": "div",
  "attributes": {
    "class": "=if(@currentField == '', if([$Evenement] == 'Formation', 'sp-css-backgroundColor-greenLight', if([$Evenement] == 'Orientation','ms-bgColor-sharedYellow10', if(@currentField == 'blocked', 'sp-css-backgroundColor-errorBackground50','transparent'))) ,if(@currentField == 'blocked', 'sp-css-backgroundColor-errorBackground50', '') )"
  },
  "children": [
    {
      "elmType": "span",
      "style": {
        "display": "inline-block",
        "padding": "0 4px"
      }
    },
    {
      "elmType": "span",
      "txtContent": "@currentField"
    }
  ]
}