White HEX code not working in Dawn slideshow background

[STextiles]

We are trying to change a slideshow background color to white using the custom CSS in the base.css section as well as the individual element code in the Customize>slideshow>custom CSS element. But when we try to do so, it doesn't effect a change, instead defaulting to grey. we've tried inputting different colours like red and teal, using a variety of methods (Hex, rgb, etc), and they work fine, but for some reason white (#ffffff) doesn't. Any advice?