An early sprite design for Miles 'Tails' Prower has been unearthed in a fresh set of 1990s SEGA and DiC design documents. The reference artwork comes from SEGA of America and was sent to DiC circa 1992, to brief the animation studio on how to illustrate Sonic's foxy friend in the 'SatAM' and 'Adventures of Sonic the Hedgehog' TV series.
Also, it shows Tails as brown. Very brown.
The discovery follows the reveal of early Tails artwork designed by several sources, including original Tails designer Yasushi Yamaguchi and Greg Martin. These sprites come from this same SatAM Sonic artwork depository, a resource that community archivist @Fieryfurnace obtained recently.
Here's what they wrote about the new find, on SSMB:
[The assets folder] also included the only colour reference DiC was sent which I’ve found so far (again, I’m assuming this would be late April 1992 based on the dates for the other Tails sheets and DiC’s character design timeline). It’s an early (perhaps the earliest?) sprite sheet of Tails for Sonic 2. This Tails is burnt orange/brown with a peach snout, chest fur, and inner ears. The tips of his tails are white, the same colour as his gloves.
Sonic fans with long memories may recall a version of Tails represented in various merchandise and other media with a peach-coloured muzzle (as opposed to the white colour we are now used to). This was no accident - Fieryfurnace posits that all of that was an accurate depiction of the character as referenced in the above reference document. You can see an image of this below, courtesy of Fieryfurnace:
While there is evidence of an artist - possibly at DiC - taking a stab at recolouring Tails, it was not until Yamaguchi's final design came in that a standardised look for Tails was set across all media (and even then, there were divergences across territories, such as on Sonic 2's Mega Drive box artwork). Fieryfurnace tracks the "origins of DiC's colour schemes for Tails" in the image below: