Same chrome-and-black base, five accent systems. Tap one, then open the live site — the choice follows you across every page on this browser until you change it. Nobody else sees this page.
Buttons, eyebrows, links, glows and the hero shader all read from the same three variables, so one choice recolours the whole site. This is the secondary accent.
Open the homepage with this scheme →Prices page:root values in /assets/theme.css and every page inherits it. The picker only changes your own browser.
Also handy: add ?theme=ember (or acid / ultraviolet / aurora / ice) to any nicell.ie URL to preview that scheme on that page. ?theme=ultraviolet resets to the default.