Example CSS for registration form on https://github.com/jphase/wordpress-custom-login-register

custom-login-register.css

/* Registration Form */
	
	#registerform p {
		margin: 10px 0;
	}
	#password-strength,
	#username-check {
		color: #fff;
		display: block;
		text-align: center;
		margin: 0 0 20px;
	}
	#registerform .bad,
	#registerform .good,
	#registerform .strong,
	#registerform .short {
		padding: 4px;
	}
	#registerform .short {
		background: #A02D00;
	}
	#registerform .bad {
		background: #A07A00;
	}
	#registerform .good {
		background: #86A000;
	}
	#registerform .strong {
		background: #00a084;
	}
	#wp-submit.disabled {
		background: #ddd;
	}