Hi,
You can change those colors within the Color Customizer => Color – UI Elements or by adding some custom CSS to Theme Options => Custom CSS.
/* WooCommerce Warnings */
.woocommerce form .form-row.woocommerce-invalid .select2-container, .woocommerce form .form-row.woocommerce-invalid input.input-text, .woocommerce form .form-row.woocommerce-invalid select, .woocommerce .woocommerce-info, .woocommerce-page .woocommerce-info {
border-color: #e9212f!important;
}
/* WooCommerce Info Message */
.woocommerce .woocommerce-message, .woocommerce-page .woocommerce-message {
border-color: #d1f2f0!important;
}
To change the icon, you can choose another icon from here: http://fontawesome.io/icons/.
For example, here is a heart: http://fontawesome.io/icon/heart/.
You can then override the CSS to change the font icon, so a heart would use this which you would add to Theme Options => Custom CSS:
.woocommerce .woocommerce-message:before, .woocommerce-page .woocommerce-message:before {
content: "\f004"!important;
color: red!important;
font-family: FontAwesome!important;
}