そうか、xyzzy.ini があったか

これで色の設定がとれますね。

(require "foreign")
(require "wip/winapi")
(c:define-dll-entry
  winapi:DWORD GetPrivateProfileString
  (winapi:LPCSTR
   winapi:LPCSTR
   winapi:LPCSTR
   winapi:LPSTR
   winapi:DWORD
   winapi:LPCSTR)
  "kernel32" "GetPrivateProfileStringA")

(defun read-ini-file (ini-f sect key default)
  (let ((csize 256))
    (let ((ini-f* (si:make-string-chunk ini-f))
          (sect* (si:make-string-chunk sect))
          (key* (si:make-string-chunk key))
          (default* (si:make-string-chunk default))
          (ret-v* (si:make-chunk nil csize)))
    (let ((ret-api-v
           (GetPrivateProfileString
            sect* key* default* ret-v* csize ini-f*)))
      (si:unpack-string ret-v* 0 ret-api-v)))))

(defun get-user-config-file-path ()
  (let ((ini-f (si:getenv "XYZZYINIFILE"))
        (ini-f-def (merge-pathnames "xyzzy.ini" (user-config-path))))
    (if (not ini-f)
        ini-f-def
      (if (not (file-exist-p ini-f))
          (if (pathname-device ini-f)
              ini-f-def
            (progn
              (setq ini-f (merge-pathnames ini-f (user-config-path)))
              (if (file-exist-p ini-f)
                  ini-f
                ini-f-def)))
        ini-f)
      )))

(defun test-read-user-config ()
  (let ((ini-f (get-user-config-file-path)))
    (read-ini-file ini-f "Colors" "kwdColor1" "")))

実行結果：

(test-read-user-config)
=>"#ff0000"