Site Title Different Color For Mobile Devices

When working on my site on the desktop, and reviewing it’s layout for a notebook, iPad, or mobile phone, the site title color is white. However, when I check my site on an actual iPad and iPhone, the site title color is black over a very dark gray background. How can I fix this to ensure the site title remains white across all devices? I’ve set colors to white where ever I can but that doesn’t help. The URL is somdcr.com and I’ve also attached is a capture from my phone so you can see the problem. Many thanks for the suggestions!