You can apply colors using predefined color names, like red, blue, green, etc. These color names represent specific colors in the CSS specification.
p { 
  color: blue; 
}
Hexadecimal colors use a combination of six hexadecimal digits (#RRGGBB) to represent a wide range of colors. Each pair of digits represents the red, green, and blue color channels.
h1 { 
  color: #FF5733; /* Bright orange */ 
}
RGB (Red, Green, Blue) colors allow you to specify the intensity of each color channel. Each channel value ranges from 0 to 255.
a { 
  color: rgb(0, 128, 0); /* Dark green */ 
}
HSL (Hue, Saturation, Lightness) colors define colors based on their position on a color wheel, their saturation level, and their lightness or darkness.
button { 
  background-color: hsl(240, 100%, 50%); /* Bright blue */ 
}
You can adjust the opacity of elements using the rgba() or hsla() syntax. The alpha channel defines transparency, with 0 being fully transparent and 1 being fully opaque.
div { 
  background-color: rgba(255, 0, 0, 0.5); /* Semi-transparent red background */ 
} 
span { 
  color: hsla(120, 100%, 50%, 0.7); /* Semi-transparent green text */ 
}