diff --git a/.gitignore b/.gitignore
index ce7aa6e6..43eebe76 100644
--- a/.gitignore
+++ b/.gitignore
@@ -69,4 +69,7 @@ gen/
 
 settings.yml
 
-node_modules/
\ No newline at end of file
+node_modules/
+
+# design files
+*.psd
diff --git a/html_app/images/Draw_Histogram_Green.png b/html_app/images/Draw_Histogram_Green.png
new file mode 100644
index 00000000..a373649c
Binary files /dev/null and b/html_app/images/Draw_Histogram_Green.png differ
diff --git a/html_app/images/Draw_Histogram_White.png b/html_app/images/Draw_Histogram_White.png
deleted file mode 100644
index 3742fb8c..00000000
Binary files a/html_app/images/Draw_Histogram_White.png and /dev/null differ
diff --git a/instructor/ui/assignment_setup.css b/instructor/ui/assignment_setup.css
index 61a0a91c..234cbba7 100644
--- a/instructor/ui/assignment_setup.css
+++ b/instructor/ui/assignment_setup.css
@@ -528,7 +528,7 @@ input[type="checkbox"].disabled {
     background-size: 25px;
 }
 .scb_ab_s_edit_white_img {
-    background: url('../images/Draw_Histogram_White.png') no-repeat;
+    background: url('../images/Draw_Histogram_Green.png') no-repeat;
     background-size: 25px;
 }