Terminator HQ Shoulderpad Colors

[appiah4]

OK, so for Terminator HQ units that are different colors than red (ie. Chaplain, Librarian, Sanguinary Priest etc.) which shoulder pad or pads get painted red?  Space Hulk's Callistarius has both pads red, for example, while older GW paintjobs have the right shoulderpad red and the newer paintjobs seem to have the left shoulderpad red.  I'm confused.

[Spyros]

Traditionally, only the right shoulder pad that has the chapter icon is in red color.

That's the way I like anyway. You can go with whatever looks better to you.

[appiah4]

I went with both red but I may switch to only right being red, not sure yet..

[Xenith]

I did both, but I went for a more obscure livery for my libby.

My chaplain only has one red.

[Majkhel]

I agree that there is much confusion in the studio painted miniatures. 
I would generally follow the rule of "allegiance" and "function" display.

The "allegiance" would be to always accurately show to which Chapter a given specialist belongs to. To that end, the shoulder pad that is to show the Chapter icon, would have a field in the Chapter Colours and appropriately coloured Chapter Badge (so black winged blood-drop on the red field for BA). Weather it will be a whole shoulder pad, or just a selected area wouldn't really matter for me. Also the shoulder pad placement would be secondary - I would usually choose the shoulder pad without the Crux Terminatus and this (usually?) limits the choice to the right one. This seems to follow the general GW studoi consensus.

Now about the Crux Terminatus shoulder pad - I usually paint it in the armour colours, as I do with the Terminators in general. It should be noted, that although sergeants deviate from this particular rule, they follow the rule of showing function with colour. In this view, I paint the Crux Terminatus shoulder pad in the specialist colours, to enhance the display of function.
This view could be supported by the few graphics from the 8th ed codex, like the Gravis Librarian who has the shoulder pad with the Librarius icon painted blue.

[Helias_Tancred]

I went with only the right one being red, but Xenith has proven you can go both red and they look awesome!

I just checked. ... scratch that. I went the Xenith route. But iircc by the book is only the right with chapter icon being red?