I want to use combination of two or more than two color as a background color of the web page or its part.
To use more than two color you can use Multicolor gradient
background-image: linear-gradient(red, yellow, green);
Linear Gradients (goes down/up/left/right/diagonally):-
To create a linear gradient you must define at least two color stops. Color stops are the colors you want to render smooth transitions among. You can also set a starting point and a direction (or an angle) along with the gradient effect.
background-image: linear-gradient(direction, color-stop1, color-stop2, ...);
Radial Gradients (defined by their center):-
A radial gradient is defined by its center.
To create a radial gradient you must also define at least two color stops.
background-image: radial-gradient(shape size at position, start-color, ..., last-color);