Change input placeholder font color

Example:

General input like newsletter on homepage:

/* -- code to change input placeholder font color -- */
input::placeholder {
color: #cc0000 !important;
}
/* - end - */

Only on forms that are on pages - Like contact page:

/* -- code to change placeholder font color on pages -- */
.template-page input::placeholder,
.template-page select,
.template-page textarea::placeholder { color: #cc0000 !important; }
/* -- end -- */

Where do I add the code?

Use this link to learn where exactly to add this code snippet:

Where to add your CSS style code