Wow, I guess it's been too long since I played MoF. I could swear I remember them being green. But it doesn't really look like Mishaguji-sama, because that had criss-crossing bullets.
Mishaguji-Sama's bullets do nod start crossing until they go a little further away from Suwako, so is's likely it's that spellcard.However, if the artist itself says it's 洩矢の鉄の輪 when it isn't, we could also say this is actually no existing spellcard at all.