If your settings file doesn't seem to be having an impact, make sure settings file is being imported BEFORE your foundation core files. This is pretty obvious when you think about it, but I had it backwards - and that won't work!
So in app.scss:
@import "_settings.scss";
@import "_custom.scss";
@import "node_modules/foundation-sites/assets/foundation";
If the settings aren't imported before the foundation core, they won't have any impact. Ditto for any customization of the settings. FYI - I'm using foundation-sites 6.4.3.

Hi. I'm having the same problem here. I've reinstalled foundation via the recommended instructions here: http://foundation.zurb.com/docs/sass.html

I've tried navigating to bower_components/modermizr post-install, and running ./bin/modernizr - I was hoping would manually build / output modernizr.js. I'm getting the following error:

module.js:338
throw err;
^
Error: Cannot find module 'lodash'
at Function.Module._resolveFilename (module.js:336:15)
at Function.Module._load (module.js:278:25)
at Module.require (module.js:365:17)
at require (module.js:384:17)
at Object. (/private/var/www/vhosts/mydomain.dev/templates/foundation/bower_components/modernizr/bin/modernizr:5:9)
at Module._compile (module.js:460:26)
at Object.Module._extensions..js (module.js:478:10)
at Module.load (module.js:355:32)
at Function.Module._load (module.js:310:12)
at Function.Module.runMain (module.js:501:10)

Hope this can help point someone in the right direction. Thanks!