I achieved some colors using \c# but no markup tags are working.
See here:

ArkMessageVector.pushBackLine("<color:FF0000>test", 0);
This is the Gui Object that manages that MessageVector:
new GuiMessageVectorCtrl(ArkChatText)
{
	profile = "ArkMLChatProfile";
	horizSizing = "right";
	vertSizing = "bottom";
	position = "1 0";
	extent = "528 256";
	minExtent = "544 128";
	enabled = "1";
	visible = "1";
	clipToParent = "1";
	lineSpacing = "0";
	lineContinuedIndex = "0";
	matchColor = "0 0 255 255";
	maxColorIndex = "9";
};
Here is the profile the GuiMessageVectorCtrl is using:
new GuiControlProfile(ArkMLChatProfile)
{
	tab = "0";
	canKeyFocus = "0";
	mouseOverSelected = "0";
	modal = "1";
	opaque = "0";
	fillColor = "200 200 200 255";
	fillColorHL = "200 200 200 255";
	fillColorNA = "200 200 200 255";
	border = "0";
	borderThickness = "1";
	borderColor = "0 0 0 255";
	borderColorHL = "128 128 128 255";
	borderColorNA = "64 64 64 255";
	fontType = "Arial";
	fontSize = "16";
	fontColors[0] = "255 0 0 255";
	fontColors[1] = "0 0 255 255";
	fontColors[2] = "0 255 0 255";
	fontColors[3] = "255 255 0 255";
	fontColors[4] = "0 255 255 255";
	fontColors[5] = "255 0 255 255";
	fontColors[6] = "255 255 255 255";
	fontColors[7] = "125 125 125 255";
	fontColors[8] = "0 0 0 255";
	fontColors[9] = "255 69 0 255";
	fontColor = "0 0 0 255";
	fontColorHL = "32 100 100 255";
	fontColorNA = "0 0 0 255";
	fontColorSEL = "200 200 200 255";
	fontColorLink = "0 0 204 255";
	fontColorLinkHL = "85 26 139 255";
	doFontOutline = "1";
	fontOutlineColor = "255 255 255 255";
	justify = "left";
	textOffset = "2 2";
	autoSizeWidth = "0";
	autoSizeHeight = "0";
	returnTab = "0";
	numbersOnly = "0";
	cursorColor = "0 0 0 255";
	bitmap = "~/client/ui/BlockWindow";
};
I don't understand what could be causing the markup tags to not work. Maybe MLText has them disabled or something?