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

CSS

1. Change color behind navigation area only

/* Keep regular color behind slider */
.featured-area{
    background-color: #425D80;
    background-image: url("images/bg-header.png");
    background-repeat: repeat;
}

/* Change color behind navigation area */
.header-wrap {background: #000;}

/* Change color behind navigation area on inside pages*/
.page-area {background: #425D80;}

2. Change the slider text color

.slide .wrap p, .slide .wrap h1, .slide .wrap h2, .slide .wrap h3, .slide .wrap h4, .slide .wrap h5, .slide .wrap h6 {color: #000;}

3. Hide page title on shop page

.template-product .content h1.page-title {
     display: none;
}