Here is how I painted the red armour of my Space Marine Heroes Blood Angel Terminator Sergeant.
Red Power Armour
Base coat the armour in Mephiston Red .
Either zenethal highlight with thinned Evil Sunz Scarlet from a downward 45 degree angle or glaze in where the light would hit.
Recess shade with Blood Angels Red thinned with Contrast Medium 1:1. Don't be too neat, the contrast should pull towards the recess and give something like a transition. Now is also a good time to paint the under-suit/tubing by your preferred method.
Recess shade everything again, this time being careful, and using thinned Rhinox Hide .
Add a chunky highlight of Evil Sunz Scarlet to all edges.
Edge highlight everything again, this time with a fine line of Wild Rider Red .
Selectively highlight extreme ages and points where highlights meet, use a 1:1 mix of Wild Rider Red and Lugganath Orange .
Add dot highlights of Lugganath Orange to the centre of the previous steps highlights and to points.
Basecoat gold parts in Liberator Gold . This may take a few coats.
Use Guilliman Flesh to coat all of the gold areas. Wick excess away where it pools, treating it like a wash.
Add small highlights to prominent areas and edges. Use a 1:1 mix of Stormhost Silver and Liberator Gold .
On points, corners and the most extreme point of prominent areas, add a dot highlight of Stormhost Silver .