No, the pranks will be there forever even if you reach the 80% obedience level, since the pranks are part of Sera's attitude and is treated as a game between the PC and her, you just diminish the chances of them happening if you invest on Sera. Now as for the pranks, they mostly happen at the ship, 2 of them happen if you access the smut button (takes 500 credits from you or leaves you with some weird porn on screen), the other while accessing your storage (messes with your items, nothing is lost) and finally the shower (transformative colouring), this prank was the exception that I was implying. The fifth prank happens at the docking bay, basically, Sera takes the ship out for a spin (it takes 2 hours for the ship to return).
In regards to the shower prank, you can skip showers altogether (dirty prick :FeelsGoodMan
, save scum before every shower at the ship, or you can simply take showers with Anno (I think that bypasses the prank), plus you have several locations that offer showers (The Gym at New Texas, The Beach on Tavros, some NPC houses). If I'm not mistaken you can also dye back your hair or body part with the hairdresser at Tavros Station, it's pretty cheap and by the time you are doing this recruitment quest you should have more than enough money for such simple modding (a Million plus). You can view Sera's lust and obedience levels through the Codex, then go to Stats, then Encounters and finally go to the Tavros section and within the Dark Chrysalis sub-section, you should find her data.