Cheapest priced copy (The List): $1.29 at Card Kingdom, near mint, their price list as of .
Cerulean Wisps 
Instant · Common · Shadowmoor · #31
Target creature becomes blue until end of turn. Untap that creature.
Draw a card.
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
2 printings · $1.29 to $34.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The List | SHM-31 | Common | $1.29 | — |
| Shadowmoor | 31 | Common | $1.49 | $34.99 |
3 rulings from Wizards of the Coast
- 1 May 2008An effect that changes a permanent’s colors overwrites all its old colors unless it specifically says “in addition to its other colors.” For example, after Cerulean Wisps resolves, the affected creature will just be blue. It doesn’t matter what colors it used to be (even if, for example, it used to be blue and black).
- 1 May 2008Changing a permanent’s color won’t change its text. If you turn Wilt-Leaf Liege blue, it will still affect green creatures and white creatures.
- 1 May 2008Colorless is not a color.