Where should I put a neutral tone in 雪白雪白?
Not all words apply neutral tone. 

雪白雪白: xuě-bái-xuě-bái 

漂漂亮亮: piào piào liang liang 

You see in 漂亮, 亮 is a neutral tone, while 白 is the second tone in 雪白. 

Checking in dictionaries is a good way to make sure you apply neutral tone correctly.