A little bit of misinformation in here. The TJ,XJ,ZJ,YJ,and CJ monotubes have always been a silver/grey color. The JK monotubes had one or two very early production runs that were clear coated zink. Now they are silver/grey also. It's the new twin tubes that will be black. The old twin tubes were silver. Also the old twin tubes were gas charged.
Another little bit of info is that all the monotubes are now made by Bilstein. Earlier non JK monotubes were made by Edelbrock. JK monotubes have always been Bilsteins. If you are not sure what you have or what you are buying look for a "B" at the end of the p/n. I.E. RXJ702B vs RXJ702.