I'm flicking through the Shaded Magic rules in Axiom 1 and I've seen the Howard and Lovecraft rules.
The Lovecraft rules state that for every point in the magic type, 2 custom powers are gained. The question is, does this stack with the cusotm powers gained for a code of conduct? So for every point, 3 custom powers are gained? That would mean 12 custom powers at 4 points in the magic type, which is crazy.
The Wizard class (right after Shades of Magic; Axioms 1, page 15) says that shaded magic was used as a code of behavior for the class.
This suggests that shaded magic should be considered a code of behavior on its own, and not stack with the codes of behavior from magic type design.
That said, given how extremely limited a Black Magic 4 character with both a 4-point code of behavior and an ‘all spells are black magic’ shading limitation would be, 12 custom powers seems like it might not be totally unreasonable. The class would be extraordinarily difficult to play.
(Note: I am not an Autarch and everything that is not a page citation is my own opinion.)
You get 1 class power per point of category value if you have a code of behavior. Shaded magic counts as a code of behavior. So a hypothetical Shaded Magic value of 4 would be worth 4 class powers.
Then, if you use the Howard rule, you get an extra class power per point of category value, so that's 8 for a Shaded Magic 4. If you use the Lovecraft rule, then you get an extra 2 class powers per point of category value, or 12 for our hypothetial Shaded Magic 4.
In the Heroic Fantasy Companion, which uses the Eldritch Magic category, it's handled as follows:
Most Eldritch casters have Eldritch 4 and get 4 class powers.
Apostasy gets you 3 eldritch spells added to your repertoire.
If you use the Howard rule, you get 4 extra class powers, all of which are automatically applied to Apostasy, yielding (4 x 3) 12 extra spells, which in turn are spent to give 2 extra spells per spell level. So basically, under the Howard rule, all Eldritch casters have their repertoire increased by 2 spells per level.
If you use the Lovercraft rule, you get 8 extra clas powers, again, all of which are automatically applied to Apostasy, yielding (8 x 3) 24 extra spells, which in turn are spent to give (24 /6) 4 extra spells per spell level. So basically, under the Lovecraft rule, all Eldritch casters have their repertoire increased by 4 spells per level.
So let's consider a hypothetical Eldritch caster with INT 16 at 1st level and 5th level . Assume he has Shaded Magic.
1st Level: His base spell repertoire as a 1st level Eldritch caster is 2 1st level spells. He gets two more for 16 INT, so his repertoire is 4 1st level spells. If he's Howardian, his repertoire is 6 1st level spells, but grey spells count as black. If he's Lovecraftian, his repertoire is 8 1st level spells, but all spells are black.
5th Level: His base spell repertoire as a 5th level Eldritch caster is 3 1st, 2 2nd, and 1 3rd level spell. He gets two more of eahc level for 16 INT, so that's 5 1st, 4 2nd, and 3 3rd. If he's Howardian, it's 7 1st, 6 2nd, and 5 3rd. If he's Lovecraftian, it's 9 1st, 8 2nd, and 7 3rd.