changing the section

today i wash the duck,rollers ect.at the yellow section i put the blak colour and at the black section i put the yellow(and re i mage only the yellow and black plate).the tinting bacground do not appear but the sfond its not the same like it was first when i print with 1.black 2.cyan 3.magenta 4.yellow like it was first but when i change the colours and the section the black look diferent over those 3 colours.tinting dont appear