Alright, after some serious delving into the librarium (read 10 min of hurried looking in my old bedroom while visiting my parents) I discovered the following.
I couldn't find anything in the rogue trader so I checked the 40k compendium (1989) and the 40k compilation (forgot to check publishing date). In the compendium is (I believe) the first space marine army list. It does not contain any scouts as an army choice and no fluff I saw regarding their armament colouring. I couldn't find anything in the original space hulk or deathwing box sets.
The first reference to scouts I have is the boxed game Space Crusade (1990). A game in which scouts board a tyranid hive ship. Although no illustrations or text regarding BA scouts, the side of the box has drawings of Ultra, SW and Emp scythe scouts. These are the old models though so they look a little different. The sergeants had power armour shoulders and the scouts had only a left shoulder pad and a metal plate on their chest which bore the squad markings.

The Ultramarines:
The chapter symbol is on everyone's left pad.
The sergeant has the devastator band triangle squad marking on his right shoulder pad.
The breast plates were white with roman numerals as squad markings on them.

The Emperor Scythes:
The chapter symbol is on everyone's left pad.
The sergeant has the devastator band triangle squad marking on his right shoulder pad.
The breast plates have a black and coloured check pattern on them as squad markings.
Numbered so:
Squad 1: white
Squad 2: red
Squad 3: green
Squad 4: dark blue
Squad 5: terracotta
Squad 6: yellow
Squad 7: grey
Squad 8: orange
Squad 9: light blue
Squad 10: dark brown

Space Wolves:
This picture was of veteran sergeant Harkon, as in the last WD. He had a cool banner which was night blue with a full moon over which is laid an upright knife and two howling wolf heads alongside it.
His left shoulder pad has yellow wolfhead with red outline on a white field, blue trim and a small iron halo. His right pad is also white with a blue trim but has a downward yellow triangle with a red tooth on it.
The scouts have a left shoulder pad which is yellow with three red teeth on it and a red rim. The chest plate have a coloured back with a white or coloured triangle varying per squad as so:
The first 5 squads have a white triangle on a black, red, yellow, blue, green background.
The next 5 squads have a white background with a black, red, yellow, blue, green triangle.

Although this is of no use to you as a blood angel, I thought it interesting to report and perhaps could be inspiring.
I then looked into the 2nd ed codex. Brother Weasel already noted above the squad markings listed in the 2nd and 3rd ed codexes and nowhere does it say these are company specific or restricted. On page 49 there is an overview of the company markings but the scout company doesn't have one. These list are again listed in the 3rd ed codex. I couldn't find any good pictures of BA scouts either so found no inspiration there.

I would therefore say that Brother Weasel's 2 lists are a safe bet to work with.

I didn't have the time to delve any deeper than that or to read closely, but I hope it helps in some way.

"Strike First, Strike Hard, NO MERCY!!"

Last Edited By: CLBenarius Nov 23 09 2:47 AM. Edited 5 times.