Change body background twentyfourteen

Your background colour is now #bbd6af, an enjoyably light teal.

I refer to the page content background which is white, i think #fffff

Are we talking about the same white background? Is this it?
https://i.imgur.com/FGHlBUA.png

All you need to do is override it in your custom CSS, like so:

.entry-header, .entry-content {
	background: red;
}

Choose any colour.

Thank you very much, i tried to add it in my style.css in my child theme, but nothing changed. Where should I add it? Here’s my style.css

@import url("../twentyfourteen/style.css");

/* Insert code below this line -------- */

@media screen and (min-width: 783px) {
	 .primary-navigation {
		 float: right;
		 margin-left: 20px;
	        }
}
.site {
		margin: 0 auto;
		}
		media screen and (min-width: 1110px) {
	.archive-header,
	.comments-area,
	.image-navigation,
	.page-header,
	.page-content,
	.post-navigation,
	.site-content .entry-header,
	.site-content .entry-content,
	.site-content .entry-summary,
	.site-content footer.entry-meta {
		padding-left: 55px;
	        }
	            }
	        .site-content .entry-header,
.site-content .entry-content,
.site-content .entry-summary,
.site-content .entry-meta,
.page-content {
		max-width: 874px;
        }
.page-content-fullwidth {
		max-width: 1200px;
        }

        .comments-area {
		max-width: 874px;
        }

        .post-navigation, .image-navigation {
		max-width: 874px;
        }

        .site:before,
#secondary {
		width: 0;
		display: none;
	    }

.featured-content {
		padding-left: 0;
        }

        .site-content, .site-main .widecolumn {
		margin-left: 0;
        }  

        .hentry {
		max-width: 900px;
        }
.post-thumbnail img {
		width: 100%;
		}  

<?php if ( function_exists( 'meteor_slideshow' ) ) { meteor_slideshow(); } ?>

Right at the bottom of your file.
And why is there Meteor Slide PHP code in your CSS file?

Dont know allready deleated it.
I added your code but it changes nothing:
I my style.css is now like this:

/*
Theme Name:     Twenty Fourteen Child
Description:    Twenty Fourteen Child Theme
Author:         Mike Simmons
Template:       twentyfourteen
*/

@import url("../twentyfourteen/style.css");

/* Insert code below this line -------- */

@media screen and (min-width: 783px) {
	 .primary-navigation {
		 float: right;
		 margin-left: 20px;
	        }
}
.site {
		margin: 0 auto;
		}
		media screen and (min-width: 1110px) {
	.archive-header,
	.comments-area,
	.image-navigation,
	.page-header,
	.page-content,
	.post-navigation,
	.site-content .entry-header,
	.site-content .entry-content,
	.site-content .entry-summary,
	.site-content footer.entry-meta {
		padding-left: 55px;
	        }
	            }
	        .site-content .entry-header,
.site-content .entry-content,
.site-content .entry-summary,
.site-content .entry-meta,
.page-content {
		max-width: 874px;
        }
.page-content-fullwidth {
		max-width: 1200px;
        }

        .comments-area {
		max-width: 874px;
        }

        .post-navigation, .image-navigation {
		max-width: 874px;
        }

        .site:before,
#secondary {
		width: 0;
		display: none;
	    }

.featured-content {
		padding-left: 0;
        }

        .site-content, .site-main .widecolumn {
		margin-left: 0;
        }  

        .hentry {
		max-width: 900px;
        }
.post-thumbnail img {
		width: 100%;
		}
.entry-header, .entry-content {
	background: red;
}

In that case, try this:

.entry-header, .entry-content {
	background: red !important;
}

Sorry I didn’t see it earlier.

Thank you so much men, it works for me!