Add spec for Terrain.MaterialColors property.

Closes #6.

Author: Anaminus

properties/MaterialColors.md

@@ -0,0 +1,47 @@
+# Terrain MaterialColors format
+This document describes the binary format of the
+[Terrain.MaterialColors][MaterialColors] property.
+
+The format of the MaterialColors property is a constant-sized array of colors.
+Each group of 3 bytes represents a Color3 value corresponding to a particular
+[Material][Material] enum item. Not all materials are represented. The 3 bytes
+in a group correspond to the red, green, and blue components of the Color3,
+respectively. The first two groups in the array appear to always be zeroed.
+
+The following table lists the nth byte in the sequence, in decimal format. Each
+row corresponds to a particular material, and the columns indicate the red
+(`RR`), green (`GG`) or blue (`BB`) component of the material's color:
+
+```text
+RR GG BB
+
+00 01 02   (reserved)
+03 04 05   (reserved)
+06 07 08   Grass
+09 10 11   Slate
+12 13 14   Concrete
+15 16 17   Brick
+18 19 20   Sand
+21 22 23   WoodPlanks
+24 25 26   Rock
+27 28 29   Glacier
+30 31 32   Snow
+33 34 35   Sandstone
+36 37 38   Mud
+39 40 41   Basalt
+42 43 44   Ground
+45 46 47   CrackedLava
+48 49 50   Asphalt
+51 52 53   Cobblestone
+54 55 56   Ice
+57 58 59   LeafyGrass
+60 61 62   Salt
+63 64 65   Limestone
+66 67 68   Pavement
+```
+
+For example, the 34th byte indicates the green component of the Sandstone
+material's color.
+
+[MaterialColors]: https://developer.roblox.com/en-us/api-reference/property/Terrain/MaterialColors
+[Material]: https://developer.roblox.com/en-us/api-reference/enum/Material