Recently added brass to my enduro and now I feel as if I need some stiffer shock springs. It currently has the stock ones that came with the builders kit. I think black springs on all 4 corners.The truck weights in at 8.4 lbs and will be adding slightly more weight to it with a brass front diff cover. My question is what does the shock springs color mean? Any suggestions on what colors I should start with and or what weigh shock oils also?. Also would not be opposed to a better shock as well. Thanks for any help in advance.