@danj and Keith Davis - I, too, am having this trouble. I have a Brother ***MFC-J5830DW*** and somehow my yellow has tank slot has become contaminated with blue ink (presumable because yellow is now green). I’ve done everything prescribed above (clean print head, Q-tip the as much contaminated blue ink as possible, changed the yellow ink tank) and still teal like green print from the yellow head. I’ve begun to clean only the yellow ‘clean head’ option in the printer and have now ‘copied’ as bright canary yellow sheet of paper on photo quality several time. Even though the out put is no longer blue - it’s light green yellowish, I feel like I’m going to have a contaminated yellow for sometime.