20 minute hack to highlight labels in assembler listings. Very limited, only suitable for the output of gcc -S or similar.

color-asm.el

(defun define-label-colors (colors)
  (loop for color in colors
  for i from 0
	for face-symbol = (intern (format "rotate-%d" i))
	do
	(custom-declare-face face-symbol
			     (list (list t (list :background color))) "")
	(set face-symbol face-symbol)))

(defvar asm-label-colors
  '("#0000cd"
    "#ff4500"
    "#528b8b"
    "#006400"
    "#8a2be2"
    "#191970"
    "#cd3700"
    "#698b22"
    "#104e8b"
    "#8b1a1a"
    "#6b8e23"
    "#27408b"
    "#5d478b"
    "#2e8b57"
    "#8b0000"
    "#4682b4"
    "#556b2f"
    "#4169e1"
    "#cd9b1d"
    "#2f4f4f"
    "#008b8b"
    "#00008b"))

(defvar asm-label-font-lock-list
  (let ((num-colors (length asm-label-colors)))
    (loop for i from 0 below num-colors collect
	  (list
	   (format "\\.L[0-9]*\\(%s\\)\\b"
		   (mapconcat 'number-to-string
			      (loop for j from i below 100 by num-colors
				    collect j)
			      "\\|"))
	   0
	   (intern (format "rotate-%d" i)) t))))

(eval-after-load "asm-mode"
  '(progn
     (define-label-colors asm-label-colors)
     (define-key asm-mode-map (kbd "C-c l") 'toggle-asm-label-colors)))

(defun asm-label-colors-on ()
  (interactive)
  (font-lock-add-keywords nil asm-label-font-lock-list)
  (font-lock-fontify-buffer))

(defun asm-label-colors-off ()
  (interactive)
  (font-lock-remove-keywords nil asm-label-font-lock-list)
  (font-lock-fontify-buffer))

(defvar asm-label-colors-enabled nil)

(defun toggle-asm-label-colors ()
  (interactive)
  (if asm-label-colors-enabled
      (asm-label-colors-off)
    (asm-label-colors-on))
  (setq asm-label-colors-enabled (not asm-label-colors-enabled)))

(provide 'color-asm)