Yellow is HP damage, pink is arousal. There is a textlog entry in the Notes section of the menu with instructions on using the juicing skill. Normally the yellow would be taken from the targets stamina, but with Bloodlust it takes from the targets health directly. (Sometimes your targets will explode into lots of little red bits from too much sex)
You'll be able to make your own traps if you grab the second trait on the LVL15 row. You'll get the "Create Trap" and "Pickup Rocks" skills, which is basically infinite traps (assuming there is no limit on player-placed traps, and that you have a good way to replenish food and stamina)