A: It is possible to multi-apply attributes to samples.  The attribute manager title bar will display which attributes are currently selected ready for attribution to samples.  To select an attribute go to the colour, shape or size tab and highlight it in the list.  Do this for any other attribute styles and then select the data in the plot window to update.

If you have other attributes selected, eg. shape or size and you just want to apply colour, then click on the highlighted shape or size entries to deselect them.