Keep in mind that what you see on your monitor screen will not exactly be the colour of the real material. A monitor screen is never a good reference for colour. You can assume the colours to be true to nature, so grass will look like grass. 

On the designs that we send, the image is shown in a neutral lightgrey box. If this appears to have a colour cast, your monitor may not have the right settings.
Below the design a greyscale is added. You should be able to see as many separate scales of grey.
If you can’t distinguish these on the right, your screen settings may be too dark. If the other way around, they may be too bright.