The present invention concerns a method for manufacturing patterned porous substrates with hidden color patterns by forming hydrophobic patterns on a hydrophilic surface, wherein structural channels are formed as a pattern in a porous substrate using a hydrophobic printing solution lacking colorant, and wherein a colored area is applied on the rear surface of the porous substrate. Further, the present invention concerns said patterned porous substrate and a method for bringing said pattern into a visible state.