You can add these CSS blocks to your Thesis -> Custom CSS screen

CSS

1. Modifying the Call to Action button color in the Primary Nav Menu

/* Change the default colors */
.cta-item.menu-item a {background-color: #000; color: #fff;}

/* Change the hover colors */
.cta-item.menu-item a:hover {background: #ccc !important; color: #000 !important;}

/* Change the active page colors */
.cta-item.menu-item a:active {background-color: #000; color: #fff;}

2. Hide site title text beside header image

#site_tagline, #site_title span.site-title {display: none !important;}

3. Add background behind testimonials section

.testimonials .wrap {width: 100%; margin: 0 auto; max-width: 1200px; display: table;overflow: hidden;}
.testimonials {background: none repeat scroll 0 0 #f0f0f0;}

4. Change color of View Work button and the hover color on home page

.portfolio-link {
    color: #fff;
    background: #000;
    opacity: .95;
}

.portfolio-link:hover {
    color: #000;
    background: #fff;
    opacity: .95;
}