The only Mordekaiser skins receiving full VFX are infernal and pentakill
According to this comment on reddit by Reav3, those will be the only skins that are receiving unique vfx that didn't have them before (KoC will also receive new effects because it had unique vfx pre-rework).
I totally understand why they made this decision, but I disagree with them. I don't think that all the skins need completely unique effects, but dragon knight and lord for sure need recolors on particles to avoid clashing color schemes. The skins will simply look bizarre without them. Please help us give Riot some feedback on this before it becomes to late to change.