Jewels on Locomotives??

I have been looking on adding some jewels on my postwar Lionel steam locomotives but am confused as to what is correct because I seem to see many configurations. I have a 1666 and it has two green but I have seen red and red with green. Is there a correct configuration?

Thanks,

Kevin

correct depends on the engine and I’m not sure what engine gets what color but they both normally would be same color if you find one red and one green I believe some one lost one at one time and a repair shop or the individual put in the other color as thats what they had.

Just looked in my repair and operating manual for Lionel 1945-1969 and it says you have the correct ones in your 1666 ( Green)

http://trn.trains.com/en/sitecore/content/Home/Railroad%20Reference/ABCs%20of%20Railroading/2006/05/Locomotive%20classification%20lights.aspx

Thanks everyone for the answers

Kevin