Short answer: Yes—eating an orange is generally allowed during Paryushan.

How to do it properly (both traditions agree on these basics):

• Orange is a tree‑fruit (not a root/kand‑mool), so it is permitted.
• Eat fresh, in the daytime, before sunset. Do not store cut fruit overnight.
• Wash well and check for tiny insects.
• Prefer the whole fruit over packaged/processed juice.

Notes by tradition:

• Shvetambar: Many take pachchakkhān to avoid kand‑mool and sometimes “bahu‑bīj” (many‑seeded) items. If you’ve taken such a vow, remove the seeds or choose seedless varieties, or avoid if your pachchakkhān says so.
• Digambar: During upavās/phalāhār, oranges are acceptable under the same rules above. Not for nirjal fasts.

If you are under a specific pachchakkhān from your guru or sangh, follow that first.