Template overrides to colorize TECPro widgets using The Events Calendar Category Colors plugin. The templates belong in {THEME}/tribe-events/widgets/ or {THEME}/tribe-events/widgets/mini-calendar/

list-widget.php

<?php
//this belongs in {THEME}/tribe-events/pro/widgets/

/**
 * Events Pro List Widget Template
 * This is the template for the output of the events list widget. 
 * All the items are turned on and off through the widget admin.
 * There is currently no default styling, which is highly needed.
 *
 * Override this template in your own theme by creating a file at [your-theme]/tribe-events/widgets/list-widget.php
 *
 * When the template is loaded, the following vars are set: $start, $end, $venue, 
 * $address, $city, $state, $province'], $zip, $country, $phone, $cost
 *
 * @package TribeEventsCalendarPro
 * @since  1.0
 * @author Modern Tribe Inc.
 *
 */

if ( !defined('ABSPATH') ) { die('-1'); } ?>

<?php 
$widget_args = tribe_events_get_adv_list_widget_args(); 
extract($widget_args);
global $post;
?>
<?php do_action( 'tribe_before_widget' ); ?>

<li>
  <h4 class="entry-title summary tribe-events-category-<?php echo current(tribe_get_event_cat_slugs($post->ID)); ?>">
		<a href="<?php echo tribe_get_event_link(); ?>" rel="bookmark"><?php the_title(); ?></a>
	</h4>
	<div class="duration">
			<?php echo tribe_events_event_schedule_details(); ?>	
	</div>
	<?php if ( $cost && tribe_get_cost() != '' ) { ?>
		<span class="tribe-events-divider">|</span>
		<div class="tribe-events-event-cost">
			<?php echo tribe_get_cost( null, true ); ?>
		</div>
	<?php } ?>			
	<div class="vcard adr location">	

		<?php if ( $venue  && tribe_get_venue() != '') { ?>
			<span class="fn org tribe-venue"><?php echo tribe_get_venue_link(); ?></span> 
		<?php } ?>

		<?php if ( $address && tribe_get_address() != '' ) { ?>
			<span class="street-address"><?php echo tribe_get_address(); ?></span>
		<?php } ?>

		<?php if ( $city && tribe_get_city() != '' ) { ?>
			<span class="locality"><?php echo tribe_get_city(); ?></span>
		<?php } ?>

		<?php if ( $region && tribe_get_region() !='' ) { ?>
			<span class="region"><?php echo tribe_get_region(); ?></span>
		<?php	} ?>

		<?php if ( $zip && tribe_get_zip() != '' ) { ?>
			<span class="postal-code"><?php echo tribe_get_zip(); ?></span>
		<?php } ?>

		<?php if ( $country  && tribe_get_country() != '') { ?>
			<span class="country-name"><?php echo tribe_get_country(); ?></span>
		<?php } ?>

		<?php if ( $organizer && tribe_get_organizer() != '' ) { ?>
		<?php _e( 'Organizer:', 'tribe-events-calendar-pro' ); ?>
				<span class="tribe-organizer"><?php echo tribe_get_organizer_link(); ?></span>
		<?php } ?>

		<?php if ( $phone && tribe_get_phone() != '' ) { ?>
			<span class="tel"><?php echo tribe_get_phone(); ?></span>
		<?php } ?>
	</div>
</li>

list.php

<?php
//this belongs in {THEME}/tribe-events/pro/widgets/mini-calendar/

 * Mini Calendar List Loop
 * This file sets up the structure for the list loop
 *
 * Override this template in your own theme by creating a file at [your-theme]/tribe-events/pro/widgets/mini-calendar/list.php
 *
 * @package TribeEventsCalendar
 * @since  3.0
 * @author Modern Tribe Inc.
 *
 */

if ( !defined('ABSPATH') ) { die('-1'); } ?>

<?php do_action( 'tribe_before_widget' ); ?>
<div class="tribe-mini-calendar-list-wrapper">
	<div class="tribe-events-loop hfeed vcalendar">

		<?php while ( have_posts() ) : the_post(); ?>
			<?php do_action('tribe_events_mini_cal_list_inside_before_loop'); ?>

			<!-- Event  -->
			<?php tribe_events_event_classes() ?>
				<?php tribe_get_template_part('pro/widgets/mini-calendar/single-event') ?>
			<!-- .hentry .vevent -->


			<?php do_action( 'tribe_events_mini_cal_list_inside_after_loop' ); ?>
		<?php endwhile; ?>

	</div><!-- .tribe-events-loop -->
</div> <!-- .tribe-mini-calendar-list-wrapper -->

single-event.php

<?php
//this belongs in {THEME}/tribe-events/pro/widgets/mini-calendar/

global $post, $wp_query;

$class = "";
if ( $wp_query->current_post == 1 ) {
  $class = ' first ';
}
if ( $wp_query->current_post+1 == $wp_query->post_count ) {
	$class .= ' last ';
}

$startDate = strtotime( $post->EventStartDate );
$endDate   = strtotime( $post->EventEndDate );
$today     = time();

/* If the event starts way in the past or ends way in the future, let's show today's date */
if ( $today > $startDate && $today < $endDate )
	$postDate = $today; else
	$postDate = $startDate;

/* If the user clicked in a particular day, let's show that day as the event date, even if the event spans a few days */
if ( defined( "DOING_AJAX" ) && DOING_AJAX && isset( $_POST['action'] ) && $_POST['action'] == 'tribe-mini-cal-day' )
	$postDate = strtotime( $_POST["eventDate"] );
?>

<div class="tribe-mini-calendar-event event-<?php echo $wp_query->current_post;?><?php echo $class;?>">
	<div class="list-date">
		<span
			class="list-dayname"><?php echo apply_filters( 'tribe-mini_helper_tribe_events_ajax_list_dayname', date( 'D', $postDate ), $postDate, $class ); ?></span>
		<span
			class="list-daynumber"><?php echo apply_filters( 'tribe-mini_helper_tribe_events_ajax_list_daynumber', date( 'd', $postDate ), $postDate, $class ); ?></span>
	</div>
	<div class="list-info">
		<h2 class="tribe-events-category-<?php echo current(tribe_get_event_cat_slugs($post->ID)); ?>"><a href="<?php echo tribe_get_event_link(); ?>"><?php echo $post->post_title; ?></a></h2>
		<?php if ( tribe_get_cost() ) { ?>
			<span class="tribe-mini-calendar-event-cost"><?php echo tribe_get_cost( null, true ); ?></span>
			<div class="tribe-events-divider ">|</div>
		<?php } ?>
		<?php echo tribe_events_event_schedule_details(); ?>
		<?php if ( tribe_get_venue() ) { ?>
			<div class="tribe-mini-calendar-event-venue">
				<?php echo tribe_get_venue_link( $post->ID ); ?>
			</div>
		<?php } ?>
	</div>
</div>

Fix for 'array to string' error

Fix for correct path pro/widgets/mini-calendar/