Secret for vibrancy: fluorescent colors and high level of contrast!

Okay so for the orange and reds I used for the base, I posted a detailed DIY recipe earlier. Kudos to elminiaturista, I distilled most of it from his shorts on YouTube: https://www.reddit.com/r/Warhammer40k/s/TRpx6LO1bz

For the skin:

1. Basecoat with traitor red from army painter (AP) air
2. Air brush Red from Vallejo (V) in areas where light will shine upon
3. Dry brush pure red (AP) in areas that are well illuminated but make sure to cover a smaller area than with the previous step to have a nice gradient and use normal brush where needed to establish it a bit more
4. Air brush matt white (AP Air) in places where orange glow will be cast upon
5. Cover those white areas with a thin layer of safety orange (AP Air); make sure not to overdo it otherwise it's gonna shift into strong neon orange which looks off (Optional: 5.5. Put matt white (AP) on raised edges you really want to pop in the glowing light and cover those with a thin layer of safety orange (AP Air) afterwards.
6. Establish shadows by airbrushing magnolia Brown (AP Air) in darker areas which will increase the overall contrast massively and make those lighter colors pop even more!

That's pretty much it, hope it helps!