Possible Clues:

• Like a stamp pad
• Like the depths
• Very dark; leaking (pen)
• One of the "Pac-Man" ghosts
• Stained; dark
• Like a messy calligrapher's hands
• Dark where US 'Derby' run?
• Like a calligrapher's fingers, at times
• Number of old Emile Zola volumes initialled, risky circling those with stained finger
• Like water surrounding a startled cuttlefish, maybe