I’ll answer in the context of standard Aṣṭa‑dravya pūjā (both Śvetāmbara & Digambar usage).

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1. What is “yellow coloured rice” (pushp)?

In Aṣṭa‑dravya:

• Akṣat = plain, unbroken white rice
• Puṣp (pushp) = the same rice, coloured yellow

Traditionally, the yellow colour is obtained by:

• Mixing the rice with a very small quantity of saffron (kesar) water

– This is the ideal and classical method.

So, “yellow coloured rice” = akṣat lightly coloured with saffron, dried properly so it is loose, not sticky.

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2. Can sandalwood or turmeric be used?

Sandalwood (chandan):

• Chandan itself is a separate dravya in Aṣṭa‑dravya.
• However, in practice many Jains:

- Take a drop of thin chandan water or very light chandan solution - Mix it with rice just to give a pale yellow tint if saffron is not available.

• This is generally accepted, provided:

- Rice remains dry and loose - You still keep the understanding that puṣp dravya is actually “yellow rice”, not chandan itself.

Turmeric (haldi):

• Not traditional for Jain Aṣṭa‑dravya puṣp.
• Problems:

- Strong, thick colour; can make the rice sticky/wet. - Is not how “pushp” is described in Jain pūjā texts (they say saffron‑coloured rice).

• If someone uses just a trace of haldi in an emergency, the main thing is bhāv (inner feeling), but:

- If you want to follow śāstriya / classical method, avoid turmeric and use saffron (or at most very light chandan water).

Summary:

• Best: saffron‑coloured rice.
• Acceptable substitute if needed: light chandan‑tinted rice.
• Turmeric is not standard; better avoided if you wish to stay close to traditional Jain pūjā-vidhi.

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3. Is arghya compulsory?

Here “arghya / argh” = mixture of all eight dravya offered together.

• In Jain dharma, no external dravya is absolutely compulsory for spiritual progress.

- The real worship is of right faith, right knowledge and right conduct and the inner purity of bhāv.

• Texts and traditional explanations say clearly:

- You may do full Aṣṭa‑dravya pūjā with arghya. - You may do only individual dravya pūjā (e.g. only jal, only chandan, etc.). - You may even worship only by reciting Navakār Mantra with pure feeling, without any external dravya at all.

So:

• Arghya is recommended and auspicious, but not compulsory.
• If you have time, space and materials, you can offer arghya.
• If not, you can still do a valid Jain pūjā with fewer dravya, or only with mantra and bhāv.

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In short:

• Yellow rice (pushp) = white rice coloured mainly with saffron.
• A little chandan water may be used to tint if saffron is not available.
• Turmeric is not the traditional Jain way; better not use it if you want to follow śāstra.
• Arghya is optional, not compulsory; inner devotion is primary.