I came across these while working on my Doctrine Novitiates (the sixth target on my 6MMRPC Hit List). Boost Markers are used to represent Boosts in Relic Knights, which are buffs you can deploy along with your units. While the markers aren't specifically tied to the available Boosts players can purchase, some of them do seem more suited for particular factions. I used that as the basis for some of the paint schemes.
The taller piece and the small container with crossed swords both struck me as identifying with the Shattered Sword Paladins, so I went with a relatively clean and white/blue scheme (VGC Wolf Grey, Electric Blue, AP Dark Tone Ink). The circular device with the skull matched the Star Nebula Corsairs symbol, so I went with a darker theme and an orange skull icon (VGC Coal Black, Wolf Grey, Orange Fire, AP Dark Tone Ink). Finally, the fourth device didn't seem faction-specific, so I went with a general-purpose black/gray scheme (VGC Coal Black, Wolf Grey, AP Dark Tone Ink). All of the bases were painted medium gray (MSP HD Concrete Gray) for a neutral color.
There are four other Boost Markers that I have to finish to complete the set. Look for them in a future post!