Can I change font and colors?

@Janette:
1. To change the font size of tagline(site description), you can go to “Appearance => Theme Options => Font Size Options” and change “Site Description Font Size”. To change the color, you can go to “Appearance => Theme Options => Color Options” and change the color code in “Site Tagline Color”
2. You can change to Green Color Scheme by Selecting “Green” from “Appearance => Theme Options = Color Options => Default Color Scheme”. Then you can change the individual color as per your need
3. For widget title and widget content, you can change the font size in the following css and add it in “Appearance => Theme Options => Custom CSS” box.

@media screen and (min-width: 961px) {
    /* For Widget Title */
    .widget-title {
        font-size: 18px;
    }
    /* For Widget Text */
    .widget-area,
    .widget ul li  {
        font-size: 14px;
    }
}

@Janette: Thanks for your appreciation.

You can add border in the slider image by adding the following css in “Appearance => Theme Options => Custom CSS” box.
#slider-wrap img { border: 1px solid #ddd; }

I am not so sure that you are talking about padding or margin. In widgets, we only have margin bottom. So, if you want to reduce or increase it then you can adjust the margin as per your need and then add it in “Appearance => Theme Options => Custom CSS” box
.widget { margin-bottom: 30px; }