their is a non-documented way that might work for text and combo boxes:
control = MB_AddPanel(null, PluginPanelDock.TextBox);
control = MB_AddPanel(null, PluginPanelDock.ComboBox);
nothing was done for labels or checkboxes
but you can detect some skin colours
Setting_GetSkinElementColour(SkinElement.SkinInputControl, ElementState.ElementStateDefault, ElementComponent.ComponentBackground);
use Color.FromArgb() to convert the number to a colour