I change background button color, but it isn't change.

Screen

Hi there,

where are you chaning the color ? In Customizer > Colors > Buttons ?

Yes Sir.
In Customizer > Colors > Buttons
Please help me, Sir.
Thank You!

Something is messing with the CSS order.

Try adding this to change the colors:

.wp-block-button__link {
    background-color: #f00;
}
/* Hover color */
.wp-block-button__link:hover {
    background-color: #00f;
}

Dear Sir,
I have solved the problem.
Thank you so much!

You're welcome