Thats because, of any color, white has the most options when it comes to picking one
Mechanical beasts, oceans made of chrome, that sort of thing
C Common Priestess with Eyes of Blue X LIGHT Level 1 [ SpellcasterTunerEffect ] ATK 0 DEF 0 When a card or effect is activated that targets this card (Quick Effect): You can send 1 Effect Monster you control to the GY, and if you do, add up to 2 "Blue-Eyes" monsters with different names from your Deck to your hand
Harmonize is a very interesting ability that allows you to tap a creature that you control to reduce the mana cost by an amount equal to its power, which means that it shouldnt be too difficult to tutor a big creature for just four green mana
Lastly, it has a Quick Effect that allows you to replace a card in the Pendulum Zone for a WATER Pendulum Monster that is in your Extra Deck or hand
What do you think