This look like an ‘open day’ sort of event, but the video describes it as a satsueikai, a photoshoot event.
You can see EF81 402 (I think this is actually 408) and EF66 20 in test liveries. I couldn’t find anything about 408’s colors, they seem nautical, I dig it. I believe Tomix made this in N as item 2135 and in HO as HO-107.
I especially like ED500-901. Hitachi built it in 1992 and JR Freight tested it until 1994. According to English Wikipedia, the design wasn’t chosen due to traction limitations. ED500-901 was on static display for some time at Hitachi’s Hitachinaka Factory, later it was scrapped.