Haha, that's the goal.

I used Daler Rowney System 3 & FW blue fluorescent inks as well as FW light green & fluorescent pink inks, Army Painter Fanatic's Arctic Gem and Wicked Pink, Vallejo MC Violet, ProAcryl Fluorescent pink, TurboDork Prism Power, and Pokorny Paints Arcane Acid.

It's mostly done with color shift paints from @turbodork.bsky.social
There's a little bit of highlighting with coloured metallics and the occasional spot of fluorescent pink/yellow/green ink in a few recesses, but it's mostly the shift paints that give the effect.

They're more daunting for my wrists and eyes than my patience haha

Over-brushing and stippling are great for open organic surfaces like that. Try a purple undercoat to increase shadow depth.

I get how daunting the freedom of open space can be, but it opens up room to embrace mistakes as features.

Thank you! I take that question as a compliment (and it's why it takes me so long).

The metallic on the brain parasite is airbrushed, but all the flat colour work (carapace, skin, etc) is handbrushed [except for an initial base coat of light blue on the fleshy bits after priming].

Totally unrelated sorry, but I just finished the Fall of Cadia and absolutely loved it. You truly captured the essence of people in impossible situations. Excellent work!

There's a lot you can do with them on the gaunt scale, whether you do the full model in them or use it only for accents.
I hope you have fun with it!

Colour shift paints work beautifully on Tyranids, I strongly recommend them. I personally use TurboDork for mine.

I don't necessarily recommend some of the fluorescent nonsense I do unless you have an airbrush and/or really enjoy glazing an obnoxious number of transparent layers. 😅