I think that Lariska should be taller than an Inika build, but shorter than the 2005 titans. I see her as a formidable opponent, but not as imposing as Roodaka.
As for colors, I think it’s likely that TTV will allow for mata green, mata blue, Metru green, and Metru blue to be used, since teal is a rare color (similar to the Artakha contest). However that said, like in the Artakha contest, it’s possible that TTV will only allow her to have one of those colors. I recommend waiting until the official rules come out, before completing your MOC, unless you plan on using Stud.io.
I think that it’s important to make the MOC fit her character. Since she is described, as an always-mobile acrobat, she should probably be not very bulky. Maybe she could have waste articulation to show her flexibility.
I’d also suggest using parts from the 2005-2006 era of bionicle, because IIRK, that’s when she appeared in the story.
If I do participate in the contest, I’ll probably include some spare knives, stored on her thighs, as I imagine Lariska to be a very skilled at combat, and prepared for any situation she might find herself in.
(Feel free to use any of the above ideas, by the way)
I’m looking forward to the Lariska contest, and I’m curious to see how people will choose to represent her mechanical arm!