True Blue Meaning

Example: Used other than as an idiom: see true,‎ blue.
1996, Richard D. Bartlett, Richard D. Bartlett, Patricia Pope Bartlet, Frogs, Toads, and Tree Frogs, page 78,
  Second, some living caerulea are blue: A few display attractive shades of blue green or, more rarely, true blue.
2010, Patti Polk, Collecting Rocks, Gems & Minerals, page 48,
  True blue chalcedony is uncommon and highly desirable as a lapidary material.
Steadfastly loyal or faithful, unwavering in loyalty.
  He was a true blue supporter, and would not listen to what he supposed to be the lies of the opposition.
2007, Lainie Speiser, Threesomes: For Couples Who Want to Know More, page 158,
  On the other hand, their swing/three-way practices have made Tony one of the most true-blue mates one could have, an absolute dream for women, in fact.
2010, Rachel Black, Blue Laws, entry in Alcohol in Popular Culture: An Encyclopedia, page 34,
  Or it may refer to “true blue” principles of Puritans—that is, unyielding and dogmatic.