Serpent's Stash part II: Besmara's Inkwell

Here's a throw-away item from 2011. That year I designed four items and debated much whether I should submit this one or whispering watcher that I ended up submitting. In 2011, I was an alt (but no-one dropped out so I didn't advance) so at least I wasn't very badly wrong about choosing the other item. Whether this item would have fared better, your guess is a good as mine.

Besmara's Inkwell
Aura faint conjuration; CL 3rd
Slot —; Price 1,000 gp; Weight —
Description
This frosted glass inkwell, usually crafted in the shape of a squid or octopus, magically refills itself each day. The ink never spills, even if the inkwell is toppled over or exposed to water.

If you hold the inkwell in hand and say aloud the name of a color, the ink immediately changes to match that color.

Once per day as a standard action, you can command the inkwell to spew forth its contents, forming a cubical 20-feet cloud of fine mist. The cloud is centered around the inkwell but remains stationary even if you move the inkwell. The cloud obscures vision just as the obscuring mist spell. Additionally, everything within the mist (except you and your belongings) is coated in a thin layer of ink, negating all benefits of invisibility. The ink cloud dissolves after three rounds, but the ink layer remains until washed off.

Unlike the obscuring mist spell, the ink cloud effect also functions underwater.
Construction
Requirements Craft Wondrous Item, glitterdust, obscuring mist, prestidigitation; Cost 500 gp

Although I hadn't quite mastered my own "recipe" for designing wondrous items back then, I think I was already on the right track. It's a bit of a SIAC, but as some people said in the "Voluntary reject bin thread", it's a good SIAC. There are a few twists there that make it slightly different from its component spells. Although it's possible to make the top 32 with SIACs with even smaller twists, I recommend going a bit farther than what I did here.

"Until washed off" seems quite vague. Sometimes it's ok to use expressions like that to save words, but when it's a very central part of the item's function, I'd recommend spelling out the rules for washing it off. If I was the GM, I suppose I would rule it's a full-round action that provokes attacks of opportunity.

I love frosted glass as a material, and I strongly recommend choosing visually interesting materials when you design wondrous items.