I plan to paint my metal-bull-daddy up as if it's being powered by multiple daemons imprisoned within it by the Chorfs.
I'm thinking of giving it one gun arm, one melee weapon arm.

The melee arm will have red/khorne flames to show the bound Khornate daemon used to grant it strength in combat.

Gun arm blue/Tzeentch flames because I'll say it fires magic drawn from the daemon powering said gun.

Gut fire will be pink or purple/Slaanesh flames as the daemon is used to grant it haste and a desire to close with the foe.

The back/top flames will green/Nurgle themed as they use the corrupting powers of the Nurgle daemon within the metal monster to corrupt the land and air around it and weaken the foe.

I hope to god it looks good lmao

I think when I get my Chorfnought I'm going to paint all the flames in different colours. Red, blue, green, purple and such.
I really like this idea because it kind of represents the idea of all the various deamons that are chained up within it. Each colour representing a certain "essence" so to speak.

The symbol on the bull's forehead reoccurs a few times across the army and is a dead ringer from the seal of Grungni that's present on all the thunderstrike models