This being fantasy I dont have to restrict myself to the traditional British heraldry rules. Colors can be broader, and should be defined by the paints available not the classic colors. Additional colors are available also. Looking at my paints I see no reason for the Bretonnians not to make a distiction between "Dark" and "Light" colors as well as Colors and Metals.
Colors
Light ColorDark Color
Ultramarine Blue#0066B3 Moridan Blue#244882
Blood Red#D2223e Scab Red#90263D
Liche Purple#2c2D8b* Purple Ink  
Codex Grey#808285 Chaos Black#001522
Goblin Green#3D9353 Dark Angel Green#19553c
Rose (Skull White + Blood Red)  Blazing Orange#E65925
Snakebite Leather#8c6c40 Scorched Brown#5a422F
* This does not look anything like the paint color.

Metals
Sunburst Yellow#FFD400
Skull White#FFFFFF
Rarely Used Metals
Burnished Gold#E0c068*
Shining Gold#EFB736*
Mithril Silver#B7BEC5*
Boltgun Metal#888791*
Dwarf Bronze#A26840*
* This does not look anything like the paint color.

Major Field Divisions and Ordinaries
Field divisions should be simple. ie paintable. No lines of division are used (no wavy, emabbtled etc). Divisions (Per...) can be a 2 metals or 2 colors. All others must be a metal and a color.
  • Horizontal
    • Per fess. Divides the field horizontal into 2 equal parts.
    • A fess. Is centered along the center line and takes up 1/3 of the field.
    • Barry. An even number of horizontal stripes. The default is 6 (3 of each tincture).
    • Cheif. From the top to 1/3 the way down.
    • Base. From the bottom to 1/3 the way up.
  • Vertical
    • Per pale. Divides the field vertically into 2 equal parts.
    • A pale. Is centered along the center line and takes up 1/3 of the field.
    • Paly. An even number of vertical stripes. The default is 6 (3 of each tincture).
  • Diagonal.
    Can be sinister also (from right to left rather than the standard from left to right).
    • Per bend. Divided into 2 part by a line that lies at a 45 degree angle from the top edge starting at the top left corner.
    • A bend. Centered along the same diagonal as a bend. The right edge starts 1/3 in from the corner, the left edge 1/3 down from the corner.
    • Bendy. An even number of diagonal stripes. The default is 6 (3 of each tincture).
  • Chevrons.
    Can be inverted.
    • Per chevron. The top point of the chevron should be above the 1/2 way point but below the 1/3rd. The lines touching the side should be as far below as the point is above.
    • A Chevron. 1/3 wide.
    • Chevrony. An even number of chevrons. The default is 6 (3 of each tincture).
  • 3 parts.
    Can be inverted.
    • Per Pall. From the top 2 corners to a spot between the 1/3 and the 1/2 line then stright down 2 metals and 1 color. Or 2 colors and 1 metal.
    • A pall. Only 1/4 as wide.
  • 4 parts.
    • Quarterly. In 4 quarters with horizontal and vertical lines.
    • Per saltire. In 4 quarters with diagonaly lines.
    • A cross. A fess intersecting a pale.
    • A saltire. A bend and a bend sinister intersecting.

Per fess...
A fess...
Barry...
A cheif...
A base...
Per pale...
A pale...
paly...
Per bend..
A bend...
Per bend sinister...
A bend sinister...
Per chevron...
A chevron...
Per chevron inverted...
A chevron inverted...
Per pall...
A pall...
Per pall inverted...
A pall inverted...
Quarterly...
A cross...
Per saltire...
A saltire...

Prophetess and Damsels
Prohpetess and Damsels always carry the banner of the Lady (Blue, a Golden Chalice and a White Border) differenced with Gold for Prophetess and White for Damsels. Difference marks can not cover the Chailce.

  • Prophetess Rowena: Blue, a border White, a Chalice Gold and 3 roundels Gold.
  • Damsel Alicia: Blue a border White, a Chalice Gold and a cheif White.
  • Damsel Isolde: Blue a border White, a Chalice Gold 2 pallets White.
  • Damsel Tova: Blue a border White, a Chalice Gold in base a crescent white. (horns point up. do a circle then cut a circle from it with the top point of both circles the same place.)

    Horses should be painted as close to the shield as possible. Do not paint horses with the same colors but a different patten than the shield. For instance if a knights blazon is Per Chevron sunburst yellow and Blood red Do not paint the horse those colors but with a horizonal line. It is acceptable to paint the front panel 1 tincture, the rear another, the head a 3rd and the reigns the rear again if the blazon is too hard to reproduce on the horse. Never paint a horse with different colors/patterns than the shield. I see lots of stuff online where the horse is red/white and the shield is gold/green. no dont do that.