Standard Highlighting

All RIDDL-aware tools—the IntelliJ plugin, VS Code extension, Synapify editor, ossum.ai playground, and this documentation site—share a common tokenization scheme for syntax highlighting. This page documents the standard token types and their associated colors.

Token Types

The RIDDL lexer classifies every span of source text into one of eleven token types, defined in the compiler's AST:

enum Token(at: At):
  case Punctuation(at: At)
  case QuotedString(at: At)
  case Readability(at: At)
  case Predefined(at: At)
  case Keyword(at: At)
  case Comment(at: At)
  case LiteralCode(at: At)
  case MarkdownLine(at: At)
  case Identifier(at: At)
  case Numeric(at: At)
  case Other(at: At)

Each token type has a specific semantic meaning:

Token Type	What It Covers	Examples
Keyword	Definition and statement keywords	domain, context, entity, handler, send, tell
Readability	Connecting words that aid readability	is, of, to, with, by, from
Predefined	Built-in type names	String, Integer, UUID, Timestamp, Boolean
Identifier	User-defined names	MyEntity, OrderPlaced, customerId
QuotedString	Double-quoted string literals	"Hello world", "application/json"
Numeric	Number literals	42, 3.14, 100
Punctuation	Structural delimiters and operators	{, }, (, ), ,, :, =
Comment	Line and block comments	// comment, /* block */
MarkdownLine	Pipe-prefixed documentation lines	\|## Heading, \|Some description text
LiteralCode	Triple-quoted code blocks	```scala ... ```
Other	Anything not classified above	Placeholder ???, unrecognized text

Standard Color Scheme

The standard RIDDL color scheme uses a dark theme as the primary palette. Each implementation adapts these colors to its platform while preserving the semantic intent.

Dark Theme

Token Type	Color	Hex	Swatch
Keyword	Burnt orange	#fa8b61	#fa8b61
Readability	Yellow-olive	#b3ae60	#b3ae60
Predefined	Teal	#19c4bf	#19c4bf
Identifier	Light gray	#a9b7c6	#a9b7c6
QuotedString	Bright green	#98c379	#98c379
Numeric	Steel blue	#6897bb	#6897bb
Punctuation	Teal	#0da19e	#0da19e
Comment	Gray (italic)	#808080	#808080
MarkdownLine	Dim green (italic)	#629755	#629755
LiteralCode	Dim green	#629755	#629755
Other	Light gray	#a9b7c6	#a9b7c6

Light Theme

Token Type	Color	Hex	Swatch
Keyword	Dark orange	#c75a20	#c75a20
Readability	Olive	#7a7a30	#7a7a30
Predefined	Teal	#0d8a85	#0d8a85
Identifier	Near black	#2b2b2b	#2b2b2b
QuotedString	Forest green	#50873a	#50873a
Numeric	Muted blue	#4a6a9a	#4a6a9a
Punctuation	Teal	#0a7a75	#0a7a75
Comment	Gray (italic)	#707070	#707070
MarkdownLine	Dark green (italic)	#3d6a30	#3d6a30
LiteralCode	Dark green	#3d6a30	#3d6a30
Other	Near black	#2b2b2b	#2b2b2b

Implementation Notes

Platform Variations

The standard colors above are the canonical reference. Individual tools may adapt them to fit their platform's conventions:

• IntelliJ IDEA Plugin — Maps token types to IntelliJ's TextAttributesKey system. Actual colors come from the user's selected theme (e.g., Darcula, IntelliJ Light) so they blend with the rest of the IDE.

• VS Code Extension — Uses TextMate scopes (e.g., keyword.control.riddl, support.type.riddl). Colors are determined by the active VS Code color theme.

• Synapify / ossum.ai Playground — These Monaco-based editors use a Catppuccin-inspired palette and split the Keyword token into semantic sub-categories (definition keywords, statement keywords, modifier keywords, etc.) for finer-grained coloring.

• This Documentation Site — Uses a custom Pygments lexer (riddl_lexer/) with CSS overrides in extra.css. The colors in the tables above are taken directly from this implementation.

Design Principles

The color scheme follows these principles:

1. Semantic grouping — Related tokens share color families (e.g., teal for types and punctuation, green for strings and documentation).

2. Keywords stand out — Burnt orange makes structural keywords immediately visible against a dark background.

3. Comments recede — Gray and italic styling keeps comments present but unobtrusive.

4. Light/dark parity — Each dark theme color has a corresponding light theme variant that maintains the same semantic associations at appropriate contrast levels.

Adding RIDDL Highlighting to a New Tool

To implement RIDDL syntax highlighting in a new editor or tool:

1. Tokenize using the eleven Token types from the enum above
2. Map each token type to your platform's highlighting system
3. Apply the standard hex colors (or your platform's closest semantic equivalent)
4. Test with both light and dark themes

The RIDDL compiler's Lexer produces these tokens directly—see com.ossuminc.riddl.language.AST.Token in the riddl repository.