diff --git a/extensions/dicom-microscopy/src/DicomMicroscopyViewport.css b/extensions/dicom-microscopy/src/DicomMicroscopyViewport.css
index 7e10bb501..db3ee2455 100644
--- a/extensions/dicom-microscopy/src/DicomMicroscopyViewport.css
+++ b/extensions/dicom-microscopy/src/DicomMicroscopyViewport.css
@@ -1,3 +1,10 @@
+.DicomMicroscopyViewer {
+  --ol-partial-background-color: rgba(127, 127, 127, 0.7);
+  --ol-foreground-color: #000000;
+  --ol-subtle-foreground-color: #000;
+  --ol-subtle-background-color: rgba(78, 78, 78, 0.5);
+}
+
 .DicomMicroscopyViewer .ol-box {
   box-sizing: border-box;
   border-radius: 2px;
@@ -332,7 +339,7 @@
 }
 
 .DicomMicroscopyViewer .ol-overviewmap-box {
-  border: 1.5px dotted var(--ol-subtle-foreground-color);
+  border: 0.5px dotted var(--ol-subtle-foreground-color);
 }
 
 .DicomMicroscopyViewer .ol-overviewmap .ol-overviewmap-box:hover {
diff --git a/extensions/dicom-microscopy/src/DicomMicroscopyViewport.tsx b/extensions/dicom-microscopy/src/DicomMicroscopyViewport.tsx
index 329760604..4c562ece1 100644
--- a/extensions/dicom-microscopy/src/DicomMicroscopyViewport.tsx
+++ b/extensions/dicom-microscopy/src/DicomMicroscopyViewport.tsx
@@ -164,7 +164,14 @@ class DicomMicroscopyViewport extends Component {
         const image = new metadataUtils.VLWholeSlideMicroscopyImage({
           metadata: inst,
         });
-        const imageFlavor = image.ImageType[2];
+
+        // NOTE: depending on different data source, image.ImageType sometimes
+        //    is a string, not a string array.
+        const imageType =
+          typeof image.ImageType === 'string'
+            ? image.ImageType.split('\\')
+            : image.ImageType;
+        const imageFlavor = imageType[2];
         if (imageFlavor === 'VOLUME' || imageFlavor === 'THUMBNAIL') {
           volumeImages.push(image);
         }