Wow. That's a strong effect for a common. Utterly frustrates some decks while being completely ignored by others. Seems more suitable for uncommon.

I like the occasional global enchantment at common. If you search gatherer for these, you find a very low number of them. There's a reason for this, like you pointed out, it's difficult to make them good, because they're hard to get rid of.

I'm concerned this might be too powerful as well, but I did choose what sounded like a powerful ability "Counter target spell..." and made it worse than Shroud. If this card only granted Shroud until end of turn, would you think it too broken? It's possible. I'm not sure what the cost for that enchantment would be.

I do know that this ability, while powerful enough to be an uncommon, is easy enough to understand that common is fine for it. This is more a matter of getting the right numbers on the thing.

Global enchantments certainly can be common. Wizards are rather down on giving repeatable effects at common at the moment, but I personally think they're overdoing that particular inclination.

I guess this probably wouldn't be too strong for common. I still think it'd be more appropriate at uncommon, but it wouldn't break very much to be common. Just make a few Limited games get a bit predictable and frustrating.

Which is true. I've been thinking about this card, and it occured to me that it's not the sort of card many people like to play with, but feel that they need to play with it for some reason or other. Why bother printing cards like that, unless the intention is to hose a specific arcetype that has gone out of control? Instead, I'm changing this card into something more player friendly... but I'm still aiming on it being a global enchantment, because I feel every set should have one at common.

Different card now. More fun? Certainly goofier, even if it is another take on control. Is the restriction that you can only change the color of spells endearing, or frustrating?

Edited again so the card now says "Target Blue Creature" and "spell or permanent" doing two things:
1). Making my previous comment make no sense, and,
2). Allowing more shenanigans for people who have access to an insane amount of mana. (Why yes, my Blue Savanah Lions has protection from your green Lightning Bolt. Let me just tap ...

Heh. It's Eight-and-a-Half Tails... but costing twice as much :P It's a fun and silly effect. (It's probably even less suitable for common than the previous one though.)

Yeah, I figured that this one isn't really a common. Combining two abilities on a card that would almost never be seen on a common does not cancel each other out. That being said, they are old and relatively simple abilities, the card isn't broken (I think) and the group that will draft this is generally a bit more sophisticated than a bunch of new Magic players, so I think I'll keep it. If I come up with a better common, though, I'll probably play swapsies.

Colouring things is fine for common: Tidal Visionary, Sisay's Ingenuity, Cloudchaser Kestrel, Aurora Griffin, and the Crimson Wisps cycle. Granting protection is a bit more dubious. But putting the two of them together grants a more powerful effect (although in this case extremely mana-expensively), which is why Eight-and-a-Half Tails and Sygg, River Guide were both rare.