My Sisters of Battle, known as the Daughters of Odin, are a very celebrated and heavy army. And they love purple!
There are a couple of purples out there in the GW world of paints. Oldest, and featured on my SoB's, is Lich highlighted up to Warlock. I find that at least one mix has to be made, if not two, to get a smooth transition.
This type of purple is the current reason I have a grudge with GW, they stopped making the basecoat for it; Midnight Blue. The weird, slightly purple tone in Midnight sets the base for Lich perfectly , and they took it away!
Other than purple, you might see a bit of turquoise. As the army grew I found out that the colors I used on my SoB's glows on the table, proof that they are holy.
The turquoise is done by basecoating with Snot Green, highlighting with Hawk Turquoise, then picking out details with Ice Blue.
Thse girls, who ride in a modified redeemer, wear a bluish-white. This is Ultrasmurf Blue, Smurf Wolf Grey and Skull White, it is also holy.
As for the big rules violation that transports my palatine and her celestians, the redeemer. First off; my codex is old, pre-redeemer old. Second; it is named a redeemer... Third; "By the Authority of the Immortal Emperor of Mankind..." (more of a fluff quote than rule). And fourth; I pay an extra 50 points to field it, only as an HQ transport.
Most importantly, as with any non-codex unit or vehicle: I inform my opponent. If my opponent has anything to say about it, such as payload, points cost, force org, etc, we talk and agree. I would not bring such a thing to a tournament.
For the cases against doing things like this, I present the opportunist gamer. The gamer who has an eye fixed to winning each game and exploiting the rules in their favor. When an opponent is presented with an army such as SoB's with a marine vehicle for no good reason (other than it kills stuff good), I object. If that rule violation was backed up by fluff, a like element (such as a squad of marines), or converted to become part of the force, I will gladly agree.
Happy Warpday...I must cut more plastic now, be well.