Jean Louis wrote:

> [0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}

Write that in Elisp and then get it font locked like this ...

(font-lock-add-keywords 'emacs-lisp-mode
 '(
   ("font-lock-builtin-face"              .  font-lock-builtin-face)
   ("font-lock-comment-delimiter-face"    .  font-lock-comment-delimiter-face)
   ("font-lock-comment-face"              .  font-lock-comment-face)
   ("font-lock-constant-face"             .  font-lock-constant-face)
   ("font-lock-doc-face"                  .  font-lock-doc-face)
   ("font-lock-function-name-face"        .  font-lock-function-name-face)
   ("font-lock-keyword-face"              .  font-lock-keyword-face)
   ("font-lock-negation-char-face"        .  font-lock-negation-char-face)
   ("font-lock-preprocessor-face"         .  font-lock-preprocessor-face)
   ("font-lock-regexp-grouping-backslash" . 'font-lock-regexp-grouping-backslash)
   ("font-lock-regexp-grouping-construct" . 'font-lock-regexp-grouping-construct)
   ("font-lock-string-face"               .  font-lock-string-face)
   ("font-lock-type-face"                 .  font-lock-type-face)
   ("font-lock-variable-name-face"        .  font-lock-variable-name-face)
   ("font-lock-warning-face"              .  font-lock-warning-face)
   )
 t)

https://dataswamp.org/~incal/figures/emacs/dressed-up-as-themselves.png