Thank you so much for your reply. I actually read some articles, which reveal that most movies tend to trick viewers into filming a sunset when in fact they should have done a sunrise. Given no further context, I know it is really hard to distinguish which is which.
Nonetheless, thank you for your tips. I will try to be more observant the next time I view photos of sunrise and sunsets. And, yes, those pink-ish and purple-ish colors are caused by pollution in the air.