SELECT 
  fontcolor, 
  backgroundcolor 
FROM 
  cscart_buynow_button 
WHERE 
  store = 1 
  OR store = 0 
ORDER BY 
  store DESC 
LIMIT 
  1

Query time 0.00011

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_buynow_button",
          "access_type": "system",
          "rows": 1,
          "filtered": 100
        }
      }
    ]
  }
}