... reminds me of Ixora brachiata, endemic to Sahyadri ranges of Western Ghats, locally known as गोरबाळे gorbale, खुरी khuri, लोखंडी lokhandi, रायकुरा raikura
The local names however are shared by other Ixora species also.
Please let know where and when were these photos taken ... in this case, may help ID better.
If these plants are in same region, colour variations may be assumed (my own assumptions !!) to depend on habitats receiving different quantum of sunlight / shade OR age of plant
... OR very simply just as your query - different species.
Regards.