Sublime Text syntax highlight setttings for Protobuf (.proto) Source: http://johnnyjacob.wordpress.com/2012/06/08/sublime-text-syntax-definition-for-google-protocol-buffers/

Protobuf.JSON-tmLanguage

{
  "name": "ProtoBuf",
  "scopeName": "source.proto",
  "fileTypes": ["proto"],
  "foldingStartMarker": "{",
  "foldingStopMarker": "}",
  "patterns": [
    { "match": "\\s+[0-9]*",
    "name": "constant.numeric.proto",
    "comment": "Field numbers"
    },
    { "match": "double|float|int32|int64|uint32|uint64|sint32|sint64|long|fixed32|fixed64|sfixed|sfixed64|bool|string|bytes",
    "name": "storage.type.source.proto",
    "comment": "Scalar Value types."
    },
    { "match": "optional|required|repeated|default",
    "name": "storage.modifier.source.proto",
    "comment": "Field Rules"
    },
    { "match": "^message|^package|^option|^import|^extend|^service",
    "name": "entity.name.function.proto",
    "comment": "Message section"
    },
    { "match": "\/\/.*",
    "name": "comment.line.double-slash.proto",
    "comment": "Comments"
    }
  ],
  "uuid": "7c5e8e41-b1b7-40e2-a140-9c0c667e1ad7"
}

Protobuf.tmLanguage

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>fileTypes</key>
	<array>
		<string>proto</string>
	</array>
	<key>foldingStartMarker</key>
	<string>{</string>
	<key>foldingStopMarker</key>
	<string>}</string>
	<key>name</key>
	<string>ProtoBuf</string>
	<key>patterns</key>
	<array>
		<dict>
			<key>comment</key>
			<string>Field numbers</string>
			<key>match</key>
			<string>\s+[0-9]*</string>
			<key>name</key>
			<string>constant.numeric.proto</string>
		</dict>
		<dict>
			<key>comment</key>
			<string>Scalar Value types.</string>
			<key>match</key>
			<string>double|float|int32|int64|uint32|uint64|sint32|sint64|long|fixed32|fixed64|sfixed|sfixed64|bool|string|bytes</string>
			<key>name</key>
			<string>storage.type.source.proto</string>
		</dict>
		<dict>
			<key>comment</key>
			<string>Field Rules</string>
			<key>match</key>
			<string>optional|required|repeated|default</string>
			<key>name</key>
			<string>storage.modifier.source.proto</string>
		</dict>
		<dict>
			<key>comment</key>
			<string>Message section</string>
			<key>match</key>
			<string>^message|^package|^option|^import|^extend|^service</string>
			<key>name</key>
			<string>entity.name.function.proto</string>
		</dict>
		<dict>
			<key>comment</key>
			<string>Comments</string>
			<key>match</key>
			<string>//.*</string>
			<key>name</key>
			<string>comment.line.double-slash.proto</string>
		</dict>
	</array>
	<key>scopeName</key>
	<string>source.proto</string>
	<key>uuid</key>
	<string>7c5e8e41-b1b7-40e2-a140-9c0c667e1ad7</string>
</dict>
</plist>