How do I change the colour scheme in DW Focus?

Hello Gab !
To change the color in the DW Focus theme: please open the template.css file in the folder path ” \wp-content\themes\dw-focus\assets\css”.
This css file contains all the code that you can change. 
Hope this helps!

– To change link color you can log in to Dashboard > Customize > Style Selector.
See the screenshot:
– To change background color for the Footer to green color, You can log in to Dashboard > Customize > General Settings , add the following code to the “Custom wp_head() code”    

<style>
#colophon.dark .container {
   background: #...;
}

#colophon.dark {   
     color: #...;
}

#colophon.dark #site-tools {     
     border-bottom-color: #FFF;
     border-top-color: #FFF;
}

#colophon.dark #sidebar-footer .widget:before {     
      background:  #FFF;
}

#colophon.dark a {    
       color: #FFF;
}

#colophon.dark .footer-shadown {
    border-bottom-color: #FFFFFF;
}
#colophon.dark #site-info {
    border-color: #FFF;
}
</style>

/**15 Must read articles */

<style>
.desktop .top-news {
     background: #...; 
}
 .desktop .top-news > a {
     color: #000000 !important;
} 
</style>   

/** Slider*/

<style>
 .news-slider {     
    background: #....;
 }
 .news-slider .carousel-list .other-entry a {
     border-bottom-color: #FFF;
    color: #FFF; 
} 
.news-slider .carousel-list .other-entry li.active a, .news-slider .carousel-list .other-entry li:hover a {
    background:  #....;
     color: #....; }
 .news-slider .carousel-list h3:after {
     border-top-color: #....;
} 
.news-slider .carousel-list h3 {
    border-bottom-color:  #....;
}
.news-slider .carousel-nav li {     background: #...;
    border-color:  #008000; 
}

 .news-slider .carousel-nav li.active a {
     background:  #....!important; 
} 
</style> 

Hope this helps !