In your case, count would be offset + current_post:
$my_query = new WP_Query(
array(
'post_type' => 'colors',
'posts_per_page' => 5,
'offset' => 2
)
);
if ( $my_query->have_posts() ) :
while ( $my_query->have_posts() ) :
$my_query->the_post();
echo $my_query->query_vars['offset'] + $my_query->current_post;
the_title();
endwhile;
endif;
wp_reset_postdata();