Skitterskin — ruling 1

Once you legally activate the ability, it doesn't matter what happens to the other colorless creature. The ability will resolve and create a regeneration shield even if you don't control another colorless creature at that time.

Skitterskin — ruling 2

Skitterskin's activated ability doesn't depend on Skitterskin being colorless. If it gains one or more colors, you can still activate the ability if you control another creature that's colorless.

Skitterskin — ruling 3

Cards with devoid use frames that are variations of the transparent frame traditionally used for Eldrazi. The top part of the card features some color over a background based on the texture of the hedrons that once imprisoned the Eldrazi. This coloration is intended to aid deckbuilding and game play.

Skitterskin — ruling 4

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

Skitterskin — ruling 5

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

Skitterskin — ruling 6

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

Skitterskin — ruling 7

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.

Skitterskin : règles, fonctionnement et interactions (MTG)

Skitterskin is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Devoid (This card has no color.) This creature can't block. : Regenerate this creature. Activate only if you control another colorless creature.

How it works : Skitterskin

Original English text — Wizards of the Coast / Scryfall

#1August 25, 2015· Wizards of the Coast
Once you legally activate the ability, it doesn't matter what happens to the other colorless creature. The ability will resolve and create a regeneration shield even if you don't control another colorless creature at that time.
No other card is named in this ruling.
#2August 25, 2015· Wizards of the Coast
Skitterskin's activated ability doesn't depend on Skitterskin being colorless. If it gains one or more colors, you can still activate the ability if you control another creature that's colorless.
No other card is named in this ruling.
#3August 25, 2015· Wizards of the Coast
Cards with devoid use frames that are variations of the transparent frame traditionally used for Eldrazi. The top part of the card features some color over a background based on the texture of the hedrons that once imprisoned the Eldrazi. This coloration is intended to aid deckbuilding and game play.
No other card is named in this ruling.
#4August 25, 2015· Wizards of the Coast
A card with devoid is just colorless. It's not colorless and the colors of mana in its mana cost.
No other card is named in this ruling.
#5August 25, 2015· Wizards of the Coast
Other cards and abilities can give a card with devoid color. If that happens, it's just the new color, not that color and colorless.
No other card is named in this ruling.
#6August 25, 2015· Wizards of the Coast
Devoid works in all zones, not just on the battlefield.
No other card is named in this ruling.
#7August 25, 2015· Wizards of the Coast
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.
No other card is named in this ruling.