I don't think this need entire plasma-desktop as dependencies & using qt6ct-kde also work if you don't use KDE Plasma and putting plasma-desktop will install unneeded packages if someone using this color scheme with qt6ct-kde

macchiato and mocha provide the same color files:

==> Cleaning up...
loading packages...
resolving dependencies...
looking for conflicting packages...

Packages (4) catppuccin-plasma-colorscheme-frappe-0.2.6-2  catppuccin-plasma-colorscheme-latte-0.2.6-2
             catppuccin-plasma-colorscheme-macchiato-0.2.6-2  catppuccin-plasma-colorscheme-mocha-0.2.6-2

Total Installed Size:  0.19 MiB

:: Proceed with installation? [Y/n] 
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error: failed to commit transaction (conflicting files)
/usr/share/color-schemes/CatppuccinMochaFlamingo.colors exists in both 'catppuccin-plasma-colorscheme-macchiato' and 'catppuccin-plasma-colorscheme-mocha'
/usr/share/color-schemes/CatppuccinMochaYellow.colors exists in both 'catppuccin-plasma-colorscheme-macchiato' and 'catppuccin-plasma-colorscheme-mocha'
Errors occurred, no packages were upgraded

Seems to be fixed as of 0.2.6-2, thanks!

The package seems to be broken, instead of placing .colors files in /usr/share/color-schemes/, it places them in the /usr/share/color-schemes/Mocha-color-schemes/ subdirectory. It also leaves a source archive at /usr/share/color-schemes/Mocha-color-schemes.tar.gz.