Sonic Triple Trouble 16-Bit and StC Stuff- Now with gallery in the 1st post

[Ultimecia]

The Mega Drive VDP supports four palettes of 16 colors each, with each color being selected from a total of 512 colors; using the Shadow/Highlight capabilities of the VDP, the total raises to 1536. Each palette is 32 bytes, with each color occupying two bytes.
The MD tile format stores two pixels in each byte. For example, if a tile byte is 0x4F, then the first pixel is color 4, and the second pixel is color 15. Note that color 0 in each palette is usually transparent, though color 0 of palette 0 is typically used for the border color.

Source: Sega Retro

It contains all the technical stuff that you might need too, so I suggest you to check out ;p