Absolutely 100% white - no shades of grey at all
All of my customer sites are SEO'd to match the Google guidelines and don't go close to anything that be classed as remotely grey (or black).
The things I find make the biggest difference, outside of ensuring the site is up to scratch, is the content. Being a copywriter, I often write entire knowledge bases for customer sites so they have a lot of unique content to share with their customers, via social media sites, to have mentioned in articles, for other sites to link to... the list goes on.
Part of this is down to the fact it is not written for the search engines, but very strong written words for visitors.
Many wont understand just what a difference this can make - coupled with a well put together site = good results.
Regards,
Andy