Eye of Ugin
Legendary Land
Colorless Eldrazi spells you cast cost 
less to cast.
, 
: Search your library for a colorless creature card, reveal it, put it into your hand, then shuffle.
Daniel Ljunggren
Rulings
Mistform Ultimus and creatures with changeling are Eldrazi. If they become colorless, possibly due to Mycosynth Lattice, Eye of Ugin would reduce the cost to cast them by {2}.
(wotc • 2013-04-15)
Eye of Ugin’s second ability lets you find any colorless creature card in your deck, such as an artifact creature card that has no colored mana symbols in its mana cost, or a creature card that’s become colorless due to Mycosynth Lattice.
(wotc • 2010-03-01)
Eye of Ugin doesn’t have a mana ability.
(wotc • 2010-03-01)
Rulings
Mistform Ultimus and creatures with changeling are Eldrazi. If they become colorless, possibly due to Mycosynth Lattice, Eye of Ugin would reduce the cost to cast them by {2}.
(wotc • 2013-04-15)
Eye of Ugin’s second ability lets you find any colorless creature card in your deck, such as an artifact creature card that has no colored mana symbols in its mana cost, or a creature card that’s become colorless due to Mycosynth Lattice.
(wotc • 2010-03-01)
Eye of Ugin doesn’t have a mana ability.
(wotc • 2010-03-01)