How to change Button color in "Header Slider" and "Sidney FP Portfolio"

Dear Sirs,

could you please explain me how to modify the color of the button in “Header Slider” ( class=“roll-button button-slider”) and also the hover color of the buttons I can create using “Sidney FP Portfolio”?

Thank you very much.

Giacomo Guarrera


Here is the code to change the button color in the slider:

.header-button {
    background-color: red;
    border: red;
    color: white;

And here is to change the hover color for the portfolio photo:

.project-thumb::before {
    background-color: rgba(255, 0, 0, .7);

You can put the code into Customizer > additional CSS.