David,
I am soo sorry.
I just saw your question about the Mimaki 604.

You can purchase the machine with or without the white option.

The white is not really white.

It bleaches (called discharge) out the color of the shirt leaving more of a very light greay than white.

I decided not to get that machine for 2 main reasons:

1) The machine with discharge greatly slows the print time.

2) I had concerns about the chemicals causing damage and wear to the
print heads, greatly shortening their lifespan.

If I get orders for dark shirts I farm them out to my screen printer.

The machine is great and the more I learn about it, the more I like it.

Greg