Input field doesn't change colour when validation doesn't match

[TerenceTanWT]

I try implementing jqBootstrapValidation on my localhost website, but I cannot get it to work as shown in the demo. I got the validation to work, and got the error message to show (e.g. not a valid email address). But I cannot get the input field to change color as shown in the demo. Does anyone knows the solution to fix the problem?