Common iron oxide powders colors&compositions

Red Iron Oxides:

FEPREN TP: α-Fe2O3 (fine powder, heat resistance up to 800 ºC)
FEPREN TD: α-Fe2O3 (very fine powder, heat resistance up to 800 ºC)

Brown Iron Oxides:

FEPREN SHD: combination of α-Fe2O3 and Fe3O4 (heat resistance approx. 120 ºC)
FEPREN HM: combination of α-Fe2O3 and MnO2 (heat resistant is up to 400 ºC)

Yellow Iron Pigment:

FEPREN Y-710: FeO(OH) (heat resistance approx. 150 ºC)

I think the best is TD-202, then TP-303.

Black Pigments:

FEPREN B: FeO . Fe2O3 (heat resistance is approx. 110 ºC.)
FEPREN BP: Fe3O4 and MnO2 (heat resistant is up to 400 ºC)

Anticorrosive Red Pigment:

JACOR Fe-1: α-Fe2O3 and Zn3(PO4)2
EDIT3: This brown opwder has surprisingly similar color to the one that Nakka used in his burnrate improver experiments. A very similar coloring indeed. Zn3(PO4)2 absorbs water up to the Zn3(PO4)2 . 4(H2O), causing crystal growth. This water may be released by heating, may bause carries substance foaming too.

SOURCE here.
their website

IMPORTANT EDIT:

Dispersibility: it is measured by several methods, but it always means something about how much work is required to disperse the bigger aglomerates of powder particles into smaller ones or into the base carrying material. Why is this important: the powder particles are of size about 0.4 micrometer, but if you try to mix the powder into oil, water or other powders, you will see that many of the small 0.4micron particles are holding together in bigger lumps.
Dispersibility may be given in scale 0-10 given the relative anount of power required to completely disperse particles, or using other test, like ISO 1524... which seems to describe how fine the agglomerates will be after some stirring time.

The conclusion is: even if we have a suitable powder, we need to apply it the most efficient way into the solid fuel.

EDIT2: Magnetite - Fe3O4: The Curie temperature of magnetite is about 580°C. Magnetite is the most magnetic of all the naturally occurring minerals on Earth, - - - question is whether 5% of magnetite could improve burnrate under high pressures so much. The moving plasma gas exiting the fuel causes electric current. Thus magnetic field could move, rotate or attract the magnetite in the molten Sugar/KN mix towards the burn zone. Note to self: examine burnrate with coil over the engine.