These are the colors (Testors) which I've found most closely match the pictures (boxes, Osprey books, etc.). For one shade colors, here are the Testors numbers; black (1149 or 1749), white (1168 or 1768), gold (1144 or 1744), silver (1146), steel (1180 or 1780), brass (1182 or 1782), flesh (flat-various available shades or mixtures). All "XF-" colors are Pactra. Testors is sold in Europe under the name "Model Master".
ALL COLOR NUMBERS ARE TESTORS UNLESS OTHERWISE STATED.
NOTE: colors based on the Osprey books-Men At Arms series #121,#129,#158,#180,#283, and #291, and the box art.

CELTIC CAVALRY
BODY PART(S)--COLOR
shirt,pants--brown,russ.earth 2124+mixed khaki+tan,ital.sand 2110+field gray 2014
chain mail,helmet--steel
shield front--white
shield back--dark tan 1742
shield rim & bar,chain mail trim--red 1150
spear--wood 1735
shield center,sword,spear tip--steel
scabbard,belt,shoes--leather 1736
helmet bird,scabbard trim,sword handle--brass
helmet plume--black
hands,face--flesh
hair, helmet horns (brown)--brown, ital. dark 2111+mixed pale yellow+black
extra shield designs--yellow,Zn Cr 1184 + steel
HORSE--whatever + black mane
blanket--red,brit.crimson 2009
blanket stripe--camouflage gray 1733
straps,saddle--leather 1736
buttons--steel
base--green 2029





GAUL WARRIORS
BODY PART(S)--COLOR
chain mail, helmet--steel
muscle cuirasse--brass
cloak--red 1150 or white
helmet feathers--red 1150 or black
helmet wings--brass
shirt (under cuirasse or mail)--brown,russ. earth 2124+camouflage gray 1733+tan,ital.sand 2110
shield back--dark tan 1742
shield front--O.D.green 1164,yellow 1169,bright blue 2032
shield design--yellow 1169,red 1150,brass
shield strap & rope--leather 1736
shield center & edge--brass
plaid pants (green shield)[base+stripe]--sky blue 1162+red,brit.crim. 2009
plaid pants (blue shield)[base+stripe]--yellow 1169+brown 1166
plaid pants (yellow shield)[base+stripe]--green 2029+green,OD 1164
horn,spear--wood 1735
body,hands,legs,face--flesh
skin shorts,belt,scabbard,shoes,ropes,chain mail shoulder pads--leather 1736
hair--brown,ital.dark 2111& mixed pale yellow
necklace,bracelet,anklet,std. animal,scabbard chain&trim,sword handle--brass
spear tips,sword--steel
base--green 2029