You have. NO idea, do you.  

one more time in some form you may understand?

If red marbles are the only ones acceptable to play on the play grounds with.  Then red marbles have value!

Other colors of marbles will only have value with just the owner of the off color marbles, and maybe other off color marble owner.  Still they can't play on the play ground.

 The red one are the ones to have!  Red ones are what you want, you get to play!

Now if the play ground changed and did not want red marbles, but now blue ones.  Red ones will become worthless.  No better than any plain old green one.  Basically worthless to all players on the play ground.

Now, I hope you can understand this explanation or you could go read one of the 20,000 books written about economics!