[Theme: Zerif Lite] Change Testimonial h6 font color

Hi,

On a site I am developing on the Zerif Lite theme I want to change the color of the Testimonial section sub heading.

I’ve done this successfully for the h2 heading using custom CSS:

.testimonial h2 {color: #000000;}

for h6 I’ve tried all of these, none of which work:

.testimonial h6 {color: #000000;}
.testimonial .section-header h6 {color: #000000;}
.testimonial .section-legend h6 {color: #000000;}
.testimonial .section-header .section-legend h6 {color: #000000;}

Have a look at the code for this section here:

<section class="testimonial" id="testimonials"><div class="container"><div class="section-header"><h2 class="white-text">Testimonials</h2><h6 class="white-text section-legend">What our clients are saying about us...</h6></div><div class="row" data-scrollreveal="enter right after 0s over 1s"><div class="col-md-12"><div id="client-feedbacks" class="owl-carousel owl-theme  "><div class="widget widget_zerif_testim-widget">
        <div class="feedback-box">

Any help appreciated.The site is here