Hi,
This theme has no support of customizer for footer copyright text. I have checked and found there is no easy way to do that.
You can override the function which writes the footer text in functions.php file [it has a chance to overwrite upon next theme update, to avoid this you can use a child theme]
Add the following function in your functions.php file,
function colormag_footer_copyright() {
$site_link = '<a href="' . esc_url( home_url( '/' ) ) . '" title="' . esc_attr( get_bloginfo( 'name', 'display' ) ) . '" ><span>' . get_bloginfo( 'name', 'display' ) . '</span></a>';
$default_footer_value = sprintf( /* Translators: %1$s: Current year, %2$s: Site link */ esc_html__( 'Copyright © %1$s %2$s. All rights reserved.', 'colormag' ), date( 'Y' ), $site_link );
$colormag_footer_copyright = '<div class="copyright">' . $default_footer_value . '</div>';
echo $colormag_footer_copyright; // phpcs:ignore WordPress.XSS.EscapeOutput.OutputNotEscaped
}
I hope this might help you.
Thanks