Changing the header nav color

Add this to your Custom CSS:

.navbar .nav > li > a { color: #fe4e03; }

.navbar .nav > li > a:focus,
.navbar .nav > li > a:hover { color: #fff; }

Unfortunately, it won’t work in Custom CSS, because the “>” is forbidden in there. You will need to make a child theme (don’t worry, it’s easy).

leading from the questions above, how can i change the colors of sub-menu backround and font?

.dropdown-menu > li > a {
color: red;
background: pink;
}

To finesse it, look in the <colour>.css theme file for all the items mentioning .dropdown-menu