If a card loses devoid, it will still be colorless. This is because effects that change an object's color (like the one created by devoid) are considered before the object loses devoid.

Each chosen mode is performed in the order specified. Abilities that trigger while one mode is being performed won't be put onto the stack until Depth Defiler's triggered ability has finished resolving.

Devoid works in all zones, not just on the battlefield.

The triggered ability will resolve before Depth Defiler does. If Depth Defiler is countered or otherwise leaves the stack in response to its triggered ability, the triggered ability will still resolve as normal. If Depth Defiler was kicked, you'll still follow the instructions of both modes.

Other cards and abilities can give a card with devoid a color. If that happens, it's just the new color, not that color and colorless.

A card with devoid is just colorless. It's not colorless and the colors of mana in its mana cost.

Devoid doesn't affect the color identity of the card for the purposes of the Commander variant. For example, while Abstruse Appropriation is colorless because it has devoid, its color identity is still white and black, and it can't be included in a Commander deck where the commander's color identity doesn't include both white and black.

The kicker ability doesn't let you pay a kicker cost more than once.

If you put a permanent with a kicker ability onto the battlefield without casting it, you can't kick it.

To determine a spell's total cost, start with the mana cost (or an alternative cost if another card's effect allows you to pay one instead), add any cost increases (such as kicker), then apply any cost reductions. The spell's mana value remains unchanged, no matter what the total cost to cast it was.

If you copy a kicked spell on the stack, the copy is also kicked. If the copied spell is a permanent spell, the token the copy of that spell becomes when it enters is also kicked.

If a spell's kicker cost was paid, the spell is "kicked."

If a card or token enters as a copy of a permanent, the new permanent isn't kicked, even if the original was.