fix(optimizer): do not convert colors inside local font names

lib/optimizer/level-1/optimize.js

@@ -37,8 +37,13 @@ var IMPORT_PREFIX_PATTERN = /^@import/i;
 var QUOTED_PATTERN = /^('.*'|".*")$/;
 var QUOTED_BUT_SAFE_PATTERN = /^['"][a-zA-Z][a-zA-Z\d\-_]+['"]$/;
 var URL_PREFIX_PATTERN = /^url\(/i;
+var LOCAL_PREFIX_PATTERN = /^local\(/i;
 var VARIABLE_NAME_PATTERN = /^--\S+$/;
 
+function isLocal(value){
+  return LOCAL_PREFIX_PATTERN.test(value);
+}
+
 function isNegative(value) {
   return value && value[1][0] == '-' && parseFloat(value[1]) < 0;
 }
@@ -443,7 +448,7 @@ function optimizeBody(rule, properties, context) {
         value = !options.compatibility.properties.urlQuotes ?
           removeUrlQuotes(value) :
           value;
-      } else if (isQuoted(value)) {
+      } else if (isQuoted(value) || isLocal(value)) {
         value = levelOptions.removeQuotes ?
           removeQuotes(name, value) :
           value;