button color

Actually, you can not directly change the standard orange color. You have to go code wise that is modify some css. So, if you want to change the color of your search button then just add this css code:

.widget_search .search-submit {
    background-color: #000000; //color of your choice
  }

Similarly, you can change color of other elements too.

Note: making a child theme for this type of code customization is always a better approach.