If you mean Paryushan/Das‑Lakshan days or the time of Samayik/Pratikraman:

• Shvetambar tradition: wear simple, clean white clothes (men: white dhoti/kurta; women: plain white sari or dress). Use a clean white muhpatti if you use one. Avoid bright/ornamental clothes, leather, silk, or wool.
• Digambar tradition: ascetics remain sky‑clad; lay followers wear plain white, simple, and non‑ornamental clothes, avoiding leather, silk, or wool.

White is preferred because it symbolizes purity and non‑attachment.