{
    "forge_marker": 1,
    "defaults": {
        "model": "minecraft:cube_bottom_top", // might be top_bottom, I don't remember. You probably need a copy of this model with all the faces specifying tintindex so that colormultiplier will work (see the gist for more info)
        "transform": "forge:default-block",
        "textures": {
            "bottom": "minecraft:blocks/diamond_block",
            "side": "minecraft:blocks/grass",
            "top": "minecraft:blocks/dirt" // set some default textures, that cascade down to all variants below
        }
    },
    "variants": {
        "facing": {
            "down": { "x": 270 },
            "up": { "x": 90 }, // 90 and 270 might be flipped, I don't remember :p
            "north": {},
            "south": { "y": 180 },
            "west": { "y": 270 },
            "east": { "y": 90 }
        },
        "type": {
            "mytypea": {
                "textures": {
                    "side": "minecraft:blocks/obsidian" // override default texture
                }
            },
            "mytypeb": {
                ...
            }
        }
    }
}