Keep last color during sequential marks

[pcrespov]

As a user I would like to highlight a set of nodes (e.g. to identify inputs and outputs of a study) by marking them with the same color. For that I add markers sequentially one node after another . Currently the default behavior is to choose a new color randomly but here I would need to "keep" the last color... whcih I would eventually might also want to change (e.g. to mark another set of nodes differently)

This behavior could be configured as part of the settings