Why are those icons black and white on my laptop and full colour on my phone?
They are all in colour on my laptop.
Perhaps you need to change the valves in your computer!
They're "emoji" - these are images that are handled like text elements ("glyphs") by the operating system, rather than rendered individually by the browser software. Windows handles them differently to MacOS, which has subtle differences to iOS, which is different again to Android, and in turn to ChromeOS and the various flavours of Linux.
The Emoji character set is still being developed - the latest update to the iOS system, for example, included a whole slew of new ones that other operating systems don't render well, or in some cases don't render at all (leaving a black outlined rectangle instead). That's why they look different on different machines.
