The idea is that once grass is chopped into planks, it starts to die and change color gradually. My suggestion would affect cosmetics only, and not have any effect on the structural integrity of the planks. It would be quite interesting to see bases built and having various parts change from bright green to dull green, grayish green, and eventually yellow depending on the age of those respective planks.   

This would be cool.  But depending on the time frame as to when they look really dull or aged.  Maybe a repair tool could bring them back to fresh looking in case the old look gets old lol.  Like a remodel without having to actually rebuild.    

I have a feeling that my suggestion would be pretty polarizing for the player base. I'm sure there are lots of players out there who wouldn't want their base to change appearance without their control. And that's understandable. Freshening up with a repair tool might be an adequate compromise for those players.