Follow instructions below to change the appearance of the su_table shortcode.

Add custom CSS class to your table

[su_table class="custom-su-table"] ... [/su_table]

Add custom CSS code at the plugin settings page

Navigate to Dashboard → Shortcodes → Settings and add the following CSS code to the Custom CSS code field:

/* Whole table */
.su-table.custom-su-table {
	border: 3px solid cyan !important;
}

/* All cells – background and text color */
.su-table.custom-su-table table td {
	background: magenta !important;
	color: white !important;
}

/* All cells – background and text color */
.su-table-alternate.custom-su-table tr:nth-child(even) td {
	background: yellow !important;
	color: black !important;
}