I think we have wandered from what the question is.
This person wants to segment with his dyed wood so is looking for penetration through the wood.
We all know that vacuum or pressure would be the way to go but he probably does not want to go that route for his own reasons.
I gather he is doing small one off jobs and just wants coloured pieces to cut and use.
I would therefore suggest porous dry woods for the coloured pieces, as previously suggest soaked in a dye to allow it to leach in through end grain.
When dried after you may well get the desired effect or drill a hole in the middle of the piece and pour the dye in the hole plugging it when finished may give a good effect to the piece.