• Pressing alt+1 now turns page into "standard sRGB" grayscale, instead of browser's default grayscale filter (same as applying completely desaturated overlay to an image in photoshop);
• Pressing Esc will bring page back to its original state;
• While in any of grayscale modes, mouse cursor turns semi-transparent.

Known issues: Sometimes page elements might visually disappear when grayscale mode turned on due to grayscale filter being applied as an SVG filter, so browser don't know what to do with it... Mostly happens to elements that have their position defined as "fixed" or "absolute".