This is how I painted the yellow and blue armour of my Craftworld Iyanden Eldar Guardian.
Basecoat all of the yellow armour with Averland Sunset .
Use Iyanden Yellow diluted with Contrast Medium , mixed 1:2 and go over all of the yellow again.
Selectively shade the deepest recesses of the armour with thinned Mournfang Brown .
Bring the plates and exposed of the armour back to the base colour by painting/glazing Averland Sunset over them again.
Chunky edge highlight of Averland Sunset and Screaming Skull mixed 2:1.
Fine edge highlight of Averland Sunset and Screaming Skull mixed 1:1.
Selective highlight of pure Screaming Skull . I would advise sticking to corners and the most prominent areas only.
Dot highlight of Screaming Skull mixed with a little pure white, like Dead White .
If at any point you are dissatisfied with the vibrancy of the yellow, I would recommend adding a little ink (like Vallejo Game Ink Yellow ) into your paint. You can then glaze over the affected area and start building up colours again.
Basecoat the helmet and and relevant areas with Macragge Blue .
Recess shade any raises detail with Kantor Blue , watered down to a glaze. This may take a couple of attempts. Alternatively, use Drakenhof Nightshade .
Chunky edge highlight of Alaitoc Blue .
Fine edge highlight of Calgar Blue .
With Calgar Blue and Blue Horror mixed 1:1, selectively highlight the most pronounced parts of edges and corners.
Place dot highlights of pure Blue Horror in corners and in the centre of the previous steps highlights.