This kit only comes in black, however the included brace is their SBL brace for AR-15, so you could replace it with this brace to get FDE: https://www.opticsplanet.com/sb-tactical-sbl-pistol-stabilizing-brace.html?_iv_color=flat-dark-earth
Yes, the adapter is compatible with virtually any AR-15 pistol grip. There are many great replacement options available through Optics Planet.
No, this is the 12/20ga version, you can find the .410 version here: https://www.opticsplanet.com/sb-tactical-410sblkit-specialty-brace-590-sbl-410-gauge-elasto-polymer-black-11.html
This is the 12/20ga version, for the .410 version you would need this one: https://www.opticsplanet.com/sb-tactical-410sblkit-specialty-brace-590-sbl-410-gauge-elasto-polymer-black-11.html
Yes, this will work on a 590M.
According to the manufacturer, this does not alter the firearm to create some other specific class of firearm. However, we cannot provide legal advice/expertise, so it is always a good idea to check with the ATF or local law enforcement before proceeding.
No, this will only fit the Mossberg 590 Shockwave.
Yes, this will fit the 20ga Shockwave as well.