Translation:Màu xanh lá cây
Hey, sorry for the late reply. There's such a long word because xanh can mean both blue and green (due to the fact the distinction to what a "color" is specifically is very blurred). The "lá cây" means "like leaves" to specify what kind of blue/green it is.
By the way, if you're wondering why the "Màu" part is necessary, it's because it's to specify that "xanh" is a color, rather than something else.
All of this information can be found in the "Tips & Notes Section". This is not available on mobile (though tbh I think it should be 'cause it's the only time grammar is usually explained.)