Could you maybe show us your entry for the ArtDefines_Civilizations and the default colors of the civs?
I should mention that it's only the secondary color that's not showing up. The primary background color is fine, but the secondary color (which had been working before the color reversal) no longer is. It just shows up as black, no matter which color scheme I test it on. Here's the xml stuff you requested:
ArtDefines File Excerpt:
<CivilizationArtInfo>
<Type>ART_DEF_CIVILIZATION_CELTS</Type> <Button>,Art/Interface/Buttons/Civilizations/Spain.dds,Art/Interface/Buttons/Warlords_Atlas_2.dds,3,1</Button>
<Path>Art/Interface/TeamColor/FlagDECAL_CelticTriskele3.dds</Path>
<bWhiteFlag>0</bWhiteFlag>
CivilizationInfos File Excerpt:
<Type>CIVILIZATION_CELT</Type>
<Description>TXT_KEY_CIV_CELT_DESC</Description>
<ShortDescription>TXT_KEY_CIV_CELT_SHORT_DESC</ShortDescription>
<Adjective>TXT_KEY_CIV_CELT_ADJECTIVE</Adjective>
<Civilopedia>TXT_KEY_CIV_CELT_PEDIA</Civilopedia>
<DefaultPlayerColor>PLAYERCOLOR_LIGHT_ORANGE</DefaultPlayerColor>
<ArtDefineTag>ART_DEF_CIVILIZATION_CELTS</ArtDefineTag>
<ArtStyleType>ARTSTYLE_EUROPEAN</ArtStyleType>
<UnitArtStyleType>UNIT_ARTSTYLE_EUROPEAN</UnitArtStyleType>
ColorInfos File Excerpt:
<PlayerColorInfo>
<Type>PLAYERCOLOR_LIGHT_ORANGE</Type>
<ColorTypePrimary>COLOR_PLAYER_LIGHT_ORANGE</ColorTypePrimary>
<ColorTypeSecondary>COLOR_PLAYER_DARK_DARK_GREEN</ColorTypeSecondary>
<TextColorType>COLOR_PLAYER_LIGHT_ORANGE_TEXT</TextColorType>
</PlayerColorInfo>