diff --git a/src/main/java/org/ntlab/citrusserver/resources/AccountsRest.java b/src/main/java/org/ntlab/citrusserver/resources/AccountsRest.java
index 90f1cae..48237dd 100644
--- a/src/main/java/org/ntlab/citrusserver/resources/AccountsRest.java
+++ b/src/main/java/org/ntlab/citrusserver/resources/AccountsRest.java
@@ -185,7 +185,7 @@
     // accountの色を返す(GET)
     @Path("/{account_id}/accountColor")
     @GET
-    @Produces(MediaType.APPLICATION_JSON)
+    @Produces(MediaType.TEXT_PLAIN)
     public String getAccountColor(@PathParam("account_id") String accountId){
         String accountColor = accountManager.getAccountColor(accountId);
         return accountColor;