When i use a rubber penis, why does my cum come out pink and red? should i be concerned? it never hurts or feels irritated, and i avoid pleasuring myself during my menstrual periods?

Pink or red implies there is some tissue trauma triggering bleeding. This may be a scuff or scrape. As long as it is minimal these usually self heal. The sensory nerve endings of the involved structures are less in number and sensitivity than your regular skin surface so you may not feel or locate the origin of the trauma.

Seems it is irritating some area inside the vagina. Best is to use it well lubricated and if it still happens get a Gyn check