I would not necessarily assume that simply because an LC is "dark" that it has not been recolored. A chemcial used by jewelers and to oxidize bronze statuary will turn copper a very dark black-brown color. In general LCs will run from steel brown to light tan with the most comon colors being steel brown, dark choc brown and olive brown. Choice pieces will show even coloration. Pieces that are splotchy or have diff colors on the field and high points should be avoided as they are generally recolored or have environmental problems. Specific issues will come in specific colors. For example, non-problem 93 Wreaths and 94s will typically run dark tan to olive brown while 96s typiocally are steel brown. Circ Classic Heads are typically steel to dark choc brown, Middle Dates typically are dark choc to med brown while Late Dates run a bit lighter.
Starting in 1797 and thru the late 1840s all cent and HC planchets came from England. First import was from Grovenors and Co, but quality was poor and the Mint switched to Boulton. Boulton supplied thru the 1840s when the Mint switched to Crocker Bros of Tauton, Mass largely on the promise of using US copper. They were caught purchasing Peruvian pig copper on the NY commodity market and a big stink ensued. By that time the copper mines in Mich began to produce sufficient copper so Crocker switched. The planchets were always "pure copper" with varying trace impurities.
As far as the Classic head cents, the planchets came from Boulton just as they had since late 1797. Some years ago a few early dates and classic head cents were tested and it was found that the classic heads were was slightly softer thus starting the myth. However, the test was limited to a very low graded junk pieces and thus shows nothing. The real reason for the overall crappy condition of most Classic Head cents is that many were melted during the War of 1812 when copper prices spiked. A record in the Annals of Congress shows that people were getting kegs of cents from the Mint and promptly selling them for their copper content to metals dealers and manufacturers. You can find an article on the mass melting of LCs and other stuff on my website -
http://user.pa.net/~hvymtl.
Edited to add: While no cents are dated 1815, cent were struck that year. With the cessation of hostilities Boulton and the Mint resumed business and the first shipment arrived Dec 10, 1815 aboard the vessel Coromadel. Cent coinage started shortly therafter as the Mint report for 1815 states that cent coinage had resumed, but no quantities were given. These cents were likely the Cornet design and dated 1816 as the Mint Director had instructed the engraver to prepare new dies earlier that year.