Why does the teacher’s “Please enter your account number” and “Please enter your password” boxes have colors but no colors are set?

Question

.txtbox{Why does the teacher's "Please enter your account" and "Please enter your password" boxes have colors but no colors are set?

border: 1px solid #bbbbbb;

width: 350px;

margin-top: 30px;

height: 50px;

padding-left: 10px;

border-radius: 5px;

}