As I am painting my Blood Angels, I keep asking myself this question: How do I distinguish each unit from the other while keeping to the Codex guides? So I started searching online and I found an impressive guide.
Extracted this from Bolter and Chainsword:
The Codex markings for BA are quoted below:
"The Blood Angel Chapter of Space Marines wear a power armoured suit of vermillion with yellow chest eagle. The Chapter badge is worn on the left shoulder and is black with a black edge trim. The exception is Sergeants who wear reversed colours - ie a black shoulder pad with red badge and trim. The right shoulder pad is also trimmed with black, although trim colours are often missed off or overpainted on campaign.
According to the Codex the Marine brothers' personal names are enscribed on the right shoulder pad, although this is not always followed and is more common amongst officers than ordinary troopers.The separate companies are denoted by the colour and number of blood drops on the right shoulder pad, positioned above the name plate where present. The exception to this is the 1st Co., which bears a yellow skull instead. Individual Squads are either distinguished by back banners of varying design or not indicated.
[right shoulder pad marks]
1st Co.: 1 yellow skull. The 1st Co. is the exception to the normal scheme and consists of all the Marines who would otherwise wear Terminator Armour. It is distinguished by the skull motif of its shoulder plate rather than the normal blood drop.
2nd Co.: 1 blue [blood drop]
3rd Co.: 1 white [blood drop]
4th Co.: 2 yellow
5th Co.: 2 blue
6th CO.: 2 white
7th Co.: 3 yellow
8th Co.: 3 blue
9th Co.: 3 white"
There is also a description and illustration of a 2nd Co Death Co marine,
"illustrating a unit which has taken the infamous blood oath of the Blood Angels.These Marines repaint their suits black with red crosses and deaths heads.."
The left shoulder pad is effectively the same as a Sergeant's pad, being black with red trim and a red BA winged blood drop. The right pad is black with red trim and a white skull and crossbones.
I can't see anything to show how this is a 2nd Co. Death Co. marine, or if this is just a fluff description: there's nothing in the listing to say that DC keep any Company or squad markings.
The Compilation also states that honour marks are displayed on the left knee, and Army/campaign markings are painted onto the right leg.
Ok, so that's the state of play as of 1991.
Coming forward to the Codex:Angels of Death, from 1996, and Codex:BA from 1998, we find a few variations. Only to be expected in a non-Codex Chapter, I suppose. As per the Codex, the current right shoulder-pad markings are:
1st Co.: 1 white skull
2nd Co.: 1 yellow [blood drop]
3rd Co.: 1 white [blood drop]
4th Co.: 1 green
5th Co.: 1 black
6th CO.: 2 yellow
7th Co.: 2 white
8th Co.: 2 green
9th Co.: 2 black
Sergeants now have yellow BA symbols on a black ground, rather than red on black. The Company badge is also now on a black ground: the trim isn't listed, but is illustrated as being red. I would imagine that 5th and 9th Co sergeants have a red ground, as black on black wouldn't work.
Individual squad types within a Company are identified by their helmet colour:
gold for Honour Guard
yellow for Veteran Assault
red for Tactical
yellow for Assault
blue for Devastator
There's also now individual squad markings listed, which are displayed on the right knee:
1st Sqd.: 1 white skull on black
2nd Sqd.: 1 white skull on blue
3rd Sqd.: 1 red blood drop on yellow
4th Sqd.: 1 red blood drop on black
5th Sqd.: 1 white cross on black
6th Sqd.: 1 white cross on blue
7th Sqd.: yellow lightning fork on black
8th Sqd.: black lightning fork on yellow
9th Sqd.: yellow wing on black
10th Sq.: black wing on yellow
You'll notice that neither book lists any 10th Company colours, which might imply that appropriate camouflage is used. Codex:BA, however, states "Blood Angels scouts are taken from the most fiery individuals in the Chapter: battle-eager warriors who hunger for close combat", which might lead one to suspect that BA would rather not wear camo, prefering the psychological advantage of hiding in the bushes wearing bright red?
And if anyone can tell me why the "battle-eager warriors who hunger for close combat" aren't in the Assault squads I'll be pleased to know. Maybe there's a jump-pack shortage or something...
The only other points of note for this guide are that the elite squad markings are defined:
Honour Guard have a black skull instead of Company markings on the right shoulder.
Veteran Assault squads have a white skull in place of their normal Company markings.
And now we move on to the 2004 "How to Paint Space Marines", which clarifies some things and muddies others, in typical GW fashion.
As far as colour scheme changes, the black border on the shoulder pad seems to have been dropped altogether, although this has been done before as a "Campaign measure".
But the main change appears to be that the chest eagle is now black, rather then the prescribed Codex yellow. All the Marines shown, HG, Tac, Dev and Assault, are shown bearing a black aquila. There is no explanation for this in the text, which seems odd for such a major change.
Oddly, the known BA successor chapters all retain the yellow aquila: the Angels Encarmine, Sanguine and Vermillion, and the Blood Drinkers. The Flesh Tearers retain their black and red scheme, but I'll let someone with more knowledge of the FT cover them.
It also gives a breakdown of the complete Chapter organization, which is in line with the 2nd edition Angels of Death codex.
1st Company: Command squad, 10 Terminator or 10 Vet Assault squads
Battle Companies (2nd thru 5th) : Command squad, 6 Tactical, 2 Assault, 2 Devastator squads
Reserve Companies (6th thru 9th):
6th: Command squad, 10 Tactical
7th: Command squad, 10 Tactical
8th: Command squad, 10 Assault
9th: Command squad, 10 Devastator
10th Scout Company: Command squad, Scout squads
Note, as far as Chapter organization, Blood Angels are identical to Codex Chapters except that their 1st Company includes Veteran Assault squads in addition to Veteran squads and Terminator squads.