MyPainter extends TextPainter
...

@Override
public void paintCell(ILayerCell cell, GC gc, Rectangle rectangle, IConfigRegistry configRegistry) {

// override the colors
IStyle style = CellStyleUtil.getCellStyle(cell, configRegistry);

cellStyle.setAttributeValue(CellStyleAttributes.FOREGROUND_COLOR, TEXT_COLOR);
cellStyle.setAttributeValue(CellStyleAttributes.BACKGROUND_COLOR, BG_COLOR);

LabelStack labelsStack = cell.getConfigLabels();
List<String> labels = labelsStack.getLabels(); //which Label do i have to use to chenge the Style, responsible for the Bg colors?

Style style = new Style();
style.setAttributeValue(CellStyleAttributes.FOREGROUND_COLOR, GUIHelper.COLOR_BLUE);
style.setAttributeValue(CellStyleAttributes.BACKGROUND_COLOR, GUIHelper.COLOR_WHITE); 

configRegistry.registerConfigAttribute(CellConfigAttributes.CELL_STYLE, style, DisplayMode.NORMAL,?WHICHLABEL?);

    @Override
    public void setupGCFromConfig(GC gc, IStyle cellStyle) {
        super.setupGCFromConfig(gc, cellStyle);
        // override own colors
        if (textColor != null) {
            gc.setForeground(textColor);
        }
        if (bgColor != null) {
            gc.setBackground(bgColor);
        }
    }