Create the ink no one's seen yet
Pilot Iroshizuku inks weren't technically designed for mixing, but you can still experiment. We mix in a clean vial, leave it a day or too to see what forms and test in a low cost pen. Low risk, high fun.
Jen's Venn
We predict potential colours by creating a Venn diagram in the Canva app.

Now the mixing
Here's the tools we used:
Pilot Hotaru-bi 50mL
Pilot Hana-ikada 50mL
Pilot Sui-gyoku 50mL
Empty ink vials
Plastic pipettes
Pocket colour wheel
My colours

If you love fountain pens, tell yourself it's OK to play. Don't wait for the perfect ink or moment to arrive. Experimentation is where the real fun lives. Your pens can handle it!