humility and Iona, Shield of Emeria choose a color spells magic

[Chameleon]

If I control humility and other player plays a Iona, Shield of Emeria, if the humility gets destroyed does he get to choose a color or is the iona ability wont do anything since no color was chosen?

[Arix]

He chooses a colour as Iona enters play. Iona's "As ~ comes into play" ability applies just before Iona actually enters play, ie just before she gets affected by Humility. Once Humility's gone, she starts banning the colour chosen.