customize bootstrap navbar color - html

Question

I have a navigation bar where I have used the bootstrap framework.
I would like to customize that navigation bar, but the bootstrap.min.css is of course impossible to read. I would fx like to change the color, font and transparency on the nav bar. Is there anybody how knows how I could do that? Can I overwrite those part of boostrap css some how? I have looked around on stackoverflow, but there is nothing that solves my problem, even if the question related to this have been up before.
Here is my navigation bar:
<nav class="navbar navbar-default navbar-fixed-top topnav" role="navigation">
<div class="container topnav">
<!-- Brand and toggle get grouped for better mobile display -->
<div class="navbar-header">
<button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand topnav" href="#">Start Bootstrap</a>
</div>
<!-- Collect the nav links, forms, and other content for toggling -->
<div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
<ul class="nav navbar-nav navbar-right">
<li>
About
</li>
<li>
Services
</li>
<li>
Contact
</li>
<!-- Login Form -->
<ul class="nav navbar-nav navbar-right">
<li class="dropdown">
<b>Login</b> <span class="caret"></span>
<ul id="login-dp" class="dropdown-menu">
<li>
<div class="row">
<div class="col-md-12">
Login via
<div class="social-buttons">
<i class="fa fa-facebook"></i> Facebook
<i class="fa fa-twitter"></i> Twitter
</div>
or
<form class="form" role="form" method="post" action="login" accept-charset="UTF-8" id="login-nav">
<div class="form-group">
<label class="sr-only" for="exampleInputEmail2">Email address</label>
<input type="email" class="form-control" id="exampleInputEmail2" placeholder="Email address" required>
</div>
<div class="form-group">
<label class="sr-only" for="exampleInputPassword2">Password</label>
<input type="password" class="form-control" id="exampleInputPassword2" placeholder="Password" required>
<div class="help-block text-right">Forget the password ?</div>
</div>
<div class="form-group">
<button type="submit" class="btn btn-primary btn-block">Sign in</button>
</div>
<div class="checkbox">
<label>
<input type="checkbox"> keep me logged-in
</label>
</div>
</form>
</div>
<div class="bottom text-center">
New here ? <b>Join Us</b>
</div>
</div>
</li>
</ul>
</li>
</ul>
<!-- /.Login Form -->
</div>
<!-- /.container -->
</nav>

Answer 1

The changing of the navbar color is relatively easy if you use the aria role="navigation".
[role="navigation"]{ background-color: #F58C14; }
You've got some bigger picture issues with regard to your bootstrap syntax. You have duplicated
<!-- Login Form -->
<ul class="nav navbar-nav navbar-right">
but you've already opened that <ul class="navbar-right a few lines up above.
You also have got the widths of the columns being specified too high. This will cause collapse issues in BOOTSTRAP when in mobile breakpoints.
Please see this fiddle for what I think you're looking for.
Dropdown side nav with aria css call

Answer 2

Ofcourse you can overwrite those styles provided by default bootstrap. But its very much advisable to overwrite them using another own custom stylesheet. When you do this always make sure your custom stylesheet is called after the bootstrap.css stylesheet.
Next questions comes how do you overwrite these styles and how do we know from which components do these styles come from. There are couple of ways to do it. Either you need to start going through the bootstrap components on their website and get used to the default classes and overwrite them -- or -- you can make use of your browser's Developer Tools (Ctrl + Shift + i in Chrome) to check which is the class which is responsible for the style and overwrite them.
Say now you want to change the navbar background color considering your example, now we know that the background color comes from the class named navbar-default from bootstrap.css. Now all we need to do is overwrite the already existing background-color coming from bootstrap stylesheet to our own color using our custom stylesheet. like so
.navbar-default {
background-color: green;
}
Hope this helps. Fiddle here