February 28, 2026

Rainbow parens, red-hot comments

Semantic Syntax Highlighting for Lisp in Emacs

Emacs gets rainbow-smart Lisp colors, and the comments explode

TLDR: A new Emacs plugin gives Lisp code smarter, meaning-aware colors and better macro support. Fans are thrilled, while skeptics worry about code-injection risks and a lively debate sparks over the inclusive README—turning a coding feature into a full-on community drama with jokes, memes, and popcorn.

Emacs just dropped a new toy for Lisp lovers: Semantic Syntax Highlighting, aka color-coding that actually understands your code. Instead of painting words blindly, it looks at what your code means, even handling those infamous Lisp macros. It’s easy to flip on via MELPA, ported from a plugin charmingly titled “colourful,” with shout-outs to Simone and misaka18931—and a proud note: Supporting Neurodiversity & Transgender & Plurality. And then the comments went full carnival.

Strongest opinion? Lisp diehards rejoiced: “Finally, colors that respect macros,” crowning it “mind-reading for parentheses.” Skeptics fired back about “code injection”—a feature used to peek into running code—asking if this would “melt my laptop” or “paint my REPL red.” The age-old Emacs vs Vim war reignited, with Vim folks posting popcorn GIFs and Emacs veterans flexing decade-old configs. A micro-drama erupted over “colourful” vs “colorful” (Brits took a polite victory lap). The biggest flare-up: the inclusive message in the README. Many cheered the rainbow, others grumbled “keep politics out of code,” prompting swift clapbacks: “People belong in tooling; kindness compiles.” Jokes flew: “My parentheses now have VIP badges,” “Emacs is living in 3020,” and one meme dubbed it the “Paren Rave.” It’s nerdy, it’s colorful, it’s peak Emacs internet energy.

Key Points

  • lisp-semantic-hl is a semantic syntax highlighting minor mode for Emacs targeting Common Lisp and Emacs Lisp.
  • Usage: load lisp-semantic-hl.el and enable lisp-semantic-hl-mode in emacs-lisp-mode or lisp-mode.
  • Installation example is provided using MELPA with use-package and hooks.
  • Goals include lexical-environment-based highlighting via CLtL2 environment inquiry APIs and better macro support.
  • The tool is ported from the LispWorks plugin ‘colourful’ and references a similar function available for Lem.

Hottest takes

"This isn’t syntax coloring, it’s mind-reading for Lisp" — parenlord
"If it injects code in my REPL, hard pass until I see audits" — cautious_cat
"Love the colors and the message—kindness compiles" — softbyte
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