Implementation issues

I am unable to recreate the Web pages taught in the HTML CSS course. I try to learn but I am unable to perform it in my code space. I am having a hard time implementing it myself.
What should I do ? How should I learn better ? It is frustrating.

<!DOCTYPE html>
<html lang="en">
    <head>
        <title>Color Marker</title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width initial-scale=1.0">
        <link rel="stylesheet" href="css/color.css">
    </head>
    <body>
        <h1>Marker</h1>
        <div class="containers">
            <div class="red">
            </div>
            <div class="green">
            </div>
            <div class="blue">
            </div>
        </div>  
    </body>
</html>
body{
    background-color: bisque;
}

h1{
    text-align: center;
    color: rgb(78, 169, 115);
}

.containers{
    background-color: darkgrey;
    padding: 10px; 
}

.red{
    background: #FF0000;
    width: 200px;
    height: 25px; 
    margin: auto;  
}
.green{
    background: rgb(50, 136, 50);
    width: 200px;
    height: 25px; 
    margin: auto;  
    padding: 2px; 
}
.blue{
    background: rgb(0, 0, 255);
    width: 200px;
    height: 25px; 
    margin: auto;
    padding: 2px;    
}

I am basically using hit and trial method. I am not able to do it with my own knowledge.
For example, Here I am not able to space the colors.

Apologies for asking not a direct, well question. I am also learning to ask the right way to ask one.

Thank You for your time.

Show us the code.
Ask for help.
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