See. It went from red w/ gold helmets to all gold apparently. Why? Because some 'eavy Metal painter had made a conversion at one point. Really though, if you look at the "new" Honour Guard, they look closer to what inspired Sanguinary Guard than what the old Honour Guard was.
With this change came a change for veterans as well. It used to be that only their company marking (white skull on right shoulder) marked them as a Veteran of the 1st Company. Now it is that they have gold helmets. But wait, that is what Honour Guards used to be. Now I have an old painted Honour Guard that are Veterans and not an Honour Guard because they don't have gold Armour but rather just helmets...
I get the change from Sanguinary Priest to Sanguinary Novitiate. The priests are heroes in their own right deserving of leading rather than following, so give an officer one in training. It allows the novitiate to learn and grants the officer council and services of the priesthood.
BUT Honour Guards lost Tech Adepts. These guys may have fit in a little weird rules wise in the past, but it made sense that an officer would have an adviser on Technical details in his inner sanctum, which the Honour Guard is supposed to be. Although it makes sense in a way to not represent the Adept in the rules. What Honour Guard would stop to wait for an Adept to fix a tank or bolster defences. None. But he is there to advise the Officer. Just because you aren't rules wise gaining the benefits of another Tech Marine does not mean that fluff wise your force commander is not gaining the insight provided by one. Plus, I am sure the Armoury would want to have someone with knowledge right next to a commander they lent rare tools to, like a vindicator.
So, what is an Honour Guard really supposed to be? Well since they aren't a permanent formation (not on the Chapter Organization page and the fluff says they pretty much are put together from whomever the captain wants at the time) I am going to go with this:
1.) Honour Guards have red armour with gold helmets. They are veterans from their company or 1st company.
2.) Maybe Dante has a permanent Honour Guard in all gold armour. But really, these guys just look like proto-Sanguinary Guard. And the ones above are clearly members of first co, as per their shoulder markings. Plus, the org does not have a permanent one listed. So MY version of his honour guard is going to be just like it was, red with gold helmets. But I would say that if you want the gold honour guard, only do it for Chapter Officials (Dante, Astorath, Epistolaries, Reclusiarchs) or 1st Company Captain. 2-10th Company Honour Guards would not be so ostentatious IMO.
3.) Though they aren't officially part of the rules anymore, I am leaving in the Tech Adept model. He is now just a veteran with what ever weapons I see fit. If you say "well what about the servo-arm?" Well, as Blood Angels you probably should have jump packs on your honour guard. BUT if you don't, there is a loop hole. Put the servo arm on and call it a power fist in your list. Then on the Tech Adept model you put 2 normal arms. One with what his other weapon is, the other holding an auspex or grenade or something. He is there for the fluff of it, not for the rules.