I’m watching TNG s4e26/s5e1 “Redemption”. There’s a scene where Worf’s honor is restored, by grabbing and bloodying Gowron’s d’k tahg. This got me thinking, Klingons absolutely adore blood rituals. Presumably, 24th century medicine makes contracting an STD a trivial issue. However, 21st century equivalent medicine would be far more limited.
This may explain Klingon blood being red sometimes and pink sometimes. Maybe one or the other is just a symptom of space syphilis.