Solved! Go to Solution.
//Style Tooltip
var cssStyleDeclarationTooltip:CSSStyleDeclaration = topLevelStyleManager.getStyleDeclaration("mx.controls.ToolTip");
if (numberOfStyleColors > 4)
{
cssStyleDeclarationTooltip.setStyle("color", textColor);
cssStyleDeclarationTooltip.setStyle("backgroundColor", backgroundColor);
}
cssStyleDeclarationTooltip.setStyle("fontSize", fontSize);
cssStyleDeclarationTooltip.setStyle("fontFamily", fontName);
topLevelStyleManager.setStyleDeclaration("mx.controls.ToolTip", cssStyleDeclarationTooltip, false);