... I find that the entirely white-coloured flowers like those posted by Gurcharan ji, are relatively rarer than the classic lilac toned.
Adding few common names that I have compiled:
bowstring hemp, crown flower, giant calotrope, giant milkweed, swallow-wort • Bengali: আকন্দ aakanda • Hindi: अर्क arka, सफ़ैद आक safed aak • Malayalam: ചുവന്നഎരിക്ക് chuvannaerikk, വെള്ളെരിക്ക് vellerikk • Manipuri: অংকোত angkot • Marathi: अर्क arka, अर्की arki, रुई rui, रुइटी ruiti • Sanskrit: alarka, अर्क arka, अर्की arki, हृस्वअग्निः hrasvagnih, सदापुष्प sadapushpa • Tamil: எருக்கு erukku, மலையெருக்கு malaiyerukku • Telugu: జిల్లేడి పువ్వు jilledi puvvu, జిల్లేడు jilledu, నల్లజిల్లేడు nallajilledu, ఉచ్చింత uccinta, ఉచ్చిత uchchinta
Regards.