Shorter URLs generally work better:
www.sample.com/bluewidgets/
www.sample.com/redwidgets/
They're still using an index.html page, because it's the default to load for a folder path, but it's omitted from the actual URL that the browser and search engine spiders see.
Be careful about using the URLs with and without the index.html at the end also or you'll dilute their
SEO value. If you don't pick one URL and stick with it everywhere, you'll end up with duplicate pages/content, which the engines won't like.