Answers for "media query css for particular width"

media query

@media only screen and (max-width: 600px) {
  body {
    background-color: lightblue;
  }
}

media query

@media only screen and (max-width: 800px) {
  body {
    background-color: ; /*your color*/
  }
}

minimum width of different devices in html

<meta name="viewport" content="width=device-width,initial-scale=1">