I have recently replaced my old gas cooker. When the new one was installed two weeks ago the flames were blue but I noticed this evening that the flames were orange. I use natural gas and I believe the flame should be blue at all times. Is there any reason why the flames would turn orange?

The air/gas mixture is off. Too much air. Have a repairperson properly calibrate your new stove especially if this is new it should be under some kind of warranty.

Is the air valve loose on the end of the burner? There is a valve that turns and has a screw to tighten it down. You may need to adjust it. Sometimes it is just dust or something around the gas that is turning it orange like rust. As long as it is not yellow it should be okay, but try adjusting it where the flame is blue and not separating from the burner holes. Too much air will lift the flame off the burner and too little air will cause it to burn yellow, which is bad. DrTom4444