Any difference's in YFZ springs between 04-07?

It looks like some springs are more of a progressive setup and others aren't...but i've seen white and yellow progressive style...are they exactly the same as eachother..just different colors?

 

From what i have seen the shocks with just the normal compression and rebound are sprung softer than the ones with the high low adjustment. I do not think that the different color springs mean anything other than to match the rest of the bike.