I offer a team calendar via Google Calendar to our sports club. It contain all match appointments for several teams and sports (like soccer, tennis, dart...). I put Unicode icons at the beginning of the subject like a dartboard and a house for a dart match at our home location and a car for outside.
Like this: 🎯🏠 DC Flight Control - Team Dart Donkies
On Smartphones the icons appears as a colored image.
In browsers on a Win7 system as a solid black icon.
On my Win10 system also as colored image.
Same Google-Account, same view, same Google-Settings...
Is this a windows depending thing? Anybody can explain?
It's a font-depending thing
Windows 7 was so old and existed long before emojis came into existence and became common, therefore it doesn't have the appropriate font to display the colored emojis. And even if you install some newer fonts then it still can't render the colored characters because its font renderer doesn't support such a new feature. Initial support for color fonts was added since Windows 8.1, but only fonts with COLR/CPAL tables. Other colored font formats were later supported in Windows 10
An update for the Segoe UI Symbol font in Windows 7 and in Windows Server 2008 R2 brought a subset of the monochrome Unicode set to those operating systems. […] Windows 8 and higher supports the full Unicode emoji characters through Microsoft's Segoe UI family of fonts. […] As of Windows 8.1 Preview, Segoe UI Emoji font supplies full-color pictographs
The same thing occurs on Linux where only a few modern distros have emoji support by default. Ubuntu has only included colored fonts since version 18.04, which means if you use the young 2-year-old Ubuntu 17.10 you'll see the black characters
Some applications like Firefox use their own font renderer and therefore can show colored emojis even on non-supported OSes. For example Firefox can display those characters on Windows 7 and Linux but Chrome and IE can't (not sure if Chrome was updated to support that or not):
Added a built-in Emoji set for operating systems without native Emoji fonts (Windows 8.0 and lower and Linux)
It's also possible that someone hates colored characters and disable it completely