add 'require' to the begin keywords

and tweak the example for the color schemes

pkgs/gui-pkgs/gui-lib/framework/private/color-prefs.rkt

@@ -597,8 +597,8 @@
   (string-append
    "#lang racket   ; draw a graph of\n"
    "(require plot) ; cos and log\n"
-   "(plot (list (function cos -5 5)\n"
-   "            (function log -5 5)))\n"
+   "(plot #:label \"y = cos(x) & y = log(x)\"\n"
+   "      (list (function cos -5 5) (function log -5 5)))\n"
    "\"an unclosed string is an error"))
 
 (struct color-scheme (name button-label white-on-black-base? mapping example) #:transparent)

pkgs/gui-pkgs/gui-lib/framework/private/main.rkt

@@ -360,7 +360,7 @@
                cond
                delay
                unit compound-unit compound-unit/sig
-               public private override
+               public private override require
                inherit sequence))
   (for-each (λ (x) (hash-set! defaults-ht x 'lambda))
             `(