Solo tienes que que añadir este CSS a tu componente de social icons y tendrás el botón de instagram con sus colores.

selector .elementor-social-icon-instagram {
    background: -webkit-radial-gradient(32% 106%, circle cover, rgb(255, 225, 125) 0%, rgb(255, 205, 105) 10%, rgb(250, 145, 55) 28%, rgb(235, 65, 65) 42%, transparent 82%), -webkit-linear-gradient(-45deg, rgb(35, 75, 215) 12%, rgb(195, 60, 190) 58%);
    background: -moz-radial-gradient(32% 106%, circle cover, rgb(255, 225, 125) 0%, rgb(255, 205, 105) 10%, rgb(250, 145, 55) 28%, rgb(235, 65, 65) 42%, transparent 82%), -moz-linear-gradient(-45deg, rgb(35, 75, 215) 12%, rgb(195, 60, 190) 58%);
    background: -ms-radial-gradient(32% 106%, circle cover, rgb(255, 225, 125) 0%, rgb(255, 205, 105) 10%, rgb(250, 145, 55) 28%, rgb(235, 65, 65) 42%, transparent 82%), -ms-linear-gradient(-45deg, rgb(35, 75, 215) 12%, rgb(195, 60, 190) 58%);
    background: -o-radial-gradient(32% 106%, circle cover, rgb(255, 225, 125) 0%, rgb(255, 205, 105) 10%, rgb(250, 145, 55) 28%, rgb(235, 65, 65) 42%, transparent 82%), -o-linear-gradient(-45deg, rgb(35, 75, 215) 12%, rgb(195, 60, 190) 58%);
    background: radial-gradient(circle farthest-corner at 32% 106%, rgb(255, 225, 125) 0%, rgb(255, 205, 105) 10%, rgb(250, 145, 55) 28%, rgb(235, 65, 65) 42%, transparent 82%), linear-gradient(135deg, rgb(35, 75, 215) 12%, rgb(195, 60, 190) 58%);
}