proto.tmLanguage

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//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>keyEquivalent</key>
  <string>^~P</string>
  <key>name</key>
  <string>Protocol Buffers</string>
  <key>patterns</key>
  <array>
    <dict>
      <key>match</key>
      <string>\b(default|enum|extend|extensions|message|option|package|rpc|returns|service)\b</string>
      <key>name</key>
      <string>keyword.operator.proto</string>
    </dict>
    <dict>
      <key>begin</key>
      <string>//</string>
      <key>end</key>
      <string>$</string>
      <key>name</key>
      <string>comment.line.double-slash.proto</string>
    </dict>
    <dict>
      <key>begin</key>
      <string>"</string>
      <key>end</key>
      <string>"</string>
      <key>name</key>
      <string>string.quoted.double.proto</string>
    </dict>
    <dict>
      <key>match</key>
      <string>\b(bool|bytes|double|fixed32|fixed64|float|int32|int64|sfixed32|sfixed64|sint32|sint64|string|uint32|uint64)\b</string>
      <key>name</key>
      <string>storage.type.proto</string>
    </dict>

    <dict>
      <key>captures</key>
      <dict>
        <key>1</key>
        <dict>
          <key>name</key>
          <string>keyword.operator.proto</string>
        </dict>
        <key>2</key>
        <dict>
          <key>name</key>
          <string>storage.type.proto</string>
        </dict>
      </dict>
      <key>match</key>
      <string>\b(repeated|required|optional)\s+(\w+)\b</string>
    </dict>
    
    <dict>
      <key>match</key>
      <string>^(import)\s</string>
      <key>name</key>
      <string>keyword.control.import.proto</string>
    </dict>
    <dict>
      <key>match</key>
      <string>\b((([0-9]+\.?[0-9]*)|(\.[0-9]+))((e|E)(\+|-)?[0-9]+)?)(L|l|F|f)?\b</string>
      <key>name</key>
      <string>constant.numeric.proto</string>
    </dict>
    <dict>
      <key>captures</key>
      <dict>
        <key>1</key>
        <dict>
          <key>name</key>
          <string>entity.name.function.proto</string>
        </dict>
      </dict>
      <key>match</key>
      <string>\b([a-zA-Z0-9_\.]*?)\(</string>
    </dict>
    <dict>
      <key>begin</key>
      <string>/\*</string>
      <key>captures</key>
      <dict>
        <key>0</key>
        <dict>
          <key>name</key>
          <string>punctuation.definition.comment.proto</string>
        </dict>
      </dict>
      <key>end</key>
      <string>\*/</string>
      <key>name</key>
      <string>comment.block.proto</string>
    </dict>
    <dict>
      <key>begin</key>
      <string>//</string>
      <key>beginCaptures</key>
      <dict>
        <key>0</key>
        <dict>
          <key>name</key>
          <string>punctuation.definition.comment.proto</string>
        </dict>
      </dict>
      <key>end</key>
      <string>$\n?</string>
      <key>name</key>
      <string>comment.line.double-slash.proto</string>
    </dict>
  </array>
  <key>scopeName</key>
  <string>source.proto</string>
  <key>uuid</key>
  <string>D6B0BFD2-F416-4E91-8C53-CD71EA3EE951</string>
</dict>
</plist>

proto.tmLanguage.json

{
    "fileTypes": [
        "proto"
    ],
    "keyEquivalent": "^~P",
    "name": "Protocol Buffers",
    "patterns": [
        {
            "match": "\\b(default|enum|extend|extensions|message|option|package|rpc|returns|service)\\b",
            "name": "keyword.operator.proto"
        },
        {
            "begin": "//",
            "end": "$",
            "name": "comment.line.double-slash.proto"
        },
        {
            "begin": "\"",
            "end": "\"",
            "name": "string.quoted.double.proto"
        },
        {
            "match": "\\b(bool|bytes|double|fixed32|fixed64|float|int32|int64|sfixed32|sfixed64|sint32|sint64|string|uint32|uint64)\\b",
            "name": "storage.type.proto"
        },
        {
            "captures": {
                "1": {
                    "name": "keyword.operator.proto"
                },
                "2": {
                    "name": "storage.type.proto"
                }
            },
            "match": "\\b(repeated|required|optional)\\s+(\\w+)\\b"
        },
        {
            "match": "^(import)\\s",
            "name": "keyword.control.import.proto"
        },
        {
            "match": "\\b((([0-9]+\\.?[0-9]*)|(\\.[0-9]+))((e|E)(\\+|-)?[0-9]+)?)(L|l|F|f)?\\b",
            "name": "constant.numeric.proto"
        },
        {
            "captures": {
                "1": {
                    "name": "entity.name.function.proto"
                }
            },
            "match": "\\b([a-zA-Z0-9_\\.]*?)\\("
        },
        {
            "begin": "/\\*",
            "captures": {
                "0": {
                    "name": "punctuation.definition.comment.proto"
                }
            },
            "end": "\\*/",
            "name": "comment.block.proto"
        },
        {
            "begin": "//",
            "beginCaptures": {
                "0": {
                    "name": "punctuation.definition.comment.proto"
                }
            },
            "end": "$\\n?",
            "name": "comment.line.double-slash.proto"
        }
    ],
    "scopeName": "source.proto",
    "uuid": "D6B0BFD2-F416-4E91-8C53-CD71EA3EE951"
}

Resources

Language Grammars & list of all scopes ( nested ):

http://manual.macromates.com/en/language_grammars#naming_conventions

Sublime plugin which convert between plist <-> json

https://github.com/facelessuser/SerializedDataConverter

Sublime Text uses Oniguruma‘s syntax for regular expressions in syntax definitions:

http://www.geocities.jp/kosako3/oniguruma/doc/RE.txt

Syntax Definitions: Sublime docs:

http://docs.sublimetext.info/en/latest/extensibility/syntaxdefs.html?highlight=syntax

---

How Syntax Definitions Work

At their core, syntax definitions are arrays of regular expressions paired with scope names. Sublime Text will try to match these patterns against a buffer’s text and attach the corresponding scope name to all occurrences. These pairs of regular expressions and scope names are known as rules.

Rules are applied in order, one line at a time. Each rule consumes the matched text region, which therefore will be excluded from the next rule’s matching attempt (save for a few exceptions). In practical terms, this means that you should take care to go from more specific rules to more general ones when you create a new syntax definition. Otherwise, a greedy regular expression might swallow parts you’d like to have styled differently.