how to do css background color

since i cant find any tutorials here's how you do this:
so let's say i wanna make green background with the word green

body {
background-color: green;
}

that's what you do, but, if that doesn't work for you, there are other options
hex colors:

body {
background-color: #00FF00;
}

then we have:
red green blue

body {
background-color: rgb(0, 255, 0);
}

and of course
red green blue alpha (transparency) [mess with the 4th number for transparency]

body {
background-color: rgba(201, 76, 76, 0.3);
}

and yeah that's it