Tapping Unknown Shores

Can someone clarify, if i tap this card http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=407691 obviously its given me one colorless Mana. But say i need to cast a spell that had 3 any color mana and One blue (for example), couldnt i tap unknown shores and use the colorless as one mana toward the "any color" part of the spell?

The reason why im asking is i also have a Blighted Fen im looking at http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=401821 and it's tap says 1 to ANY color mana. To me both cards do the same thing

Thank you in advance