Can you switch Sparkling hues freely?

Switching only covers hues you have already unlocked. A new hue still comes from a reroll. Using a Sparkling Cube on a sparkling Aniimo gives it a random colour, and you cannot choose which one. On a Prismana Aniimo that reroll can even land on a colour it already had, or one very close to it.

That is the problem version 1.1 fixes. Before it, a reroll was a gamble on the look you had. Now every hue you unlock stays available, so a bad roll costs you nothing you cannot swap straight back to. The regular colour counts too: an Aniimo you made Sparkling with a Sparkling Cube can return to its normal look at any time.

For Prismana Aniimo, the original Prismana hue is treated as an unlocked hue. Use a Sparkling Cube on one and you can still switch back to its Prismana colour afterwards, along with any sparkling hues it has picked up.

Not settled: How Sparkling Cubes relate to Prismana is not settled. They are treated both as an item for catching Prismana and as one used on Prismana you already own to change their hue.