when a card says something along the lines of creatures cost 2 less to cast for blah blah reason and the 2 is colorless... does this mean if the cost includes color it will be covered or that it only accounts for colorless mana in a cost? in other words will the 2 less only count if colorless is in the cost or will it cover even specific colored mana cost?
It usually only counts as generic mana. For instance, if you have two {Goblin Electromancer}s out, {Mana Leak} still costs you a blue mana. If the cost is reduced by colored mana, it will tell you, like in {Chord of Calling}.
If it shows 2 colorless it is only 2 colorless cheaper. If it were to cost 1{R}, it would end up costing you {R}
Have a look at the {heartless summoning} deck in articles to see how it works. I've given the natural cost and the adjusted cost for each creature I play. :)