Quick answer: Unreal Niagara InitializeParticle module's Color not applied to the first spawn frame? Module runs after spawn; first frame uses default - move color setting to Spawn module.
Per-particle color set in Initialize. First few frames: default white. Eventually correct.
Set color in Spawn
Move the color logic to a Spawn module. Applies before the first draw.
Or pre-cache
Set as User Parameter; particle reads at spawn. Immediate; no module ordering.
Verify per-frame
Pause VFX at frame 0; check color. Default = the ordering bug.
“Niagara modules run in order. Initialize is later than Spawn for some properties.”
If you see one-frame default-color flashes, the module ordering is the cause. Spawn > Initialize for color.