Slider button colour

Love the Lightning theme!
Really clean and beautiful design with useful functions.
Please can you help me change the colour of the previous and next buttons on the home page slide show? I’d like to make it blue #3a69aa so that it is visible against both white and black slider images. Here’s what I’ve tried already:

• Cutomising Colors
• Looking for settings in Lightning Home page slide show, Lightning Design Settings
• Additional CSS

• swiper-navigation-color: #3a69aa;
• swiper-button-white: #3a69aa;
• swiper-theme-color: #3a69aa;

• Looking for the relevant settings or images in the theme’s CSS etc.

Please help. I’d change the colour of the slide images but white and black really suit the site. Thank you.

The page I need help with: [log in to see the link]