1.The World produced a rainbow.
I can see the rainbow
2.The rainbow is offered  to  my eye.
The eye does not collect colours. It collects electromagnetic radiations to which the organ of sight reacts. They are located between infra-red rays and ultraviolet rays which are extreme frequencies not visible to the human eye and correspond to red colors for the lowest ones and violet  for the highest ones.

All the rainbow's colours are in a range of waves acceptable to my eye.

If my vision were programmed as the one of a bee, I would collect only the ultraviolet rays and I wouldn't see the rainbow.
And yet! That wouldn't prevent it from existing!

Fondamental estate can exist without references to objects which  have  significant appearance to us.

3. My eye uses the rainbow to reveal it to my body with the source  of my brain.
If it's impossible to get one's consciousness raised without the human brain, it's because it's up to consciousness to appear in the human brain.
Thus, consciousness can exist without the brain  having itself, a significant and material existence.
Are you curious?