Components failing cannot cause a problem were black looks a bit too brown. A lamp getting old cannot do something that specific either. You could have too little blue light from the lamp but that would make EVERYTHING look too yellow or too brown (dark). This is digital video. You don't have things affecting the 1s and 0s selectively and intelligently... which is what would have to happen for your particular problem to happen. When a component fails, you lose the entire integrity of the 1s and 0s and end up with a completely trashed picture. Even something in the light path that is failing can't really cause a problem you describe as it would affect blue (or red and green) in all luminance (brightness) ranges, not just the darker shades of yellow (browns). Red + Green = yellow when red and green are bright or = brown when red and green are dimmer.
JVC projectors, depending on vintage, may have controls that can fix your specific problem, but you're not likely to fix it yourself without an understanding of calibration and calibration controls and the controls available in your specific projector (the newer the JVC projector, the more useful the internal calibration controls are, the older it is, the less precision you will have from the internal calibration controls). So the right fix for your issue is for you to teach yourself how to calibrate and acquire a suitable meter, software, and test pattern source or hire a professional who is familiar with JVC projector calibration for your vintage (someone not experienced can probably figure out the controls, but it could take quite a while, probably more than 1 day's work. Someone experienced with your year/model would get the projector calibrated as well as it can be calibrated in a single trip.