Hi Akshay Katore,
For changing the color of your page you need to open the properties of the page and in style section you can set the background-color: #####; like this.
By using this css property you can change the color of page.
Hope this helps you.
I would not reccomend placing styling information within the specific pages. What a general good idea is, is to adjust the colors within your SASS folder of your application.
Mendix folder > Theme > Styles > Web > Sass > App > _custom-variables.scss
This file includes all colors used within your application and allows you to change the colors:
See below picture of some variables that will help you. Find these in the file in your folder
In order to run changes and see them locally, do use CALYPSO: