Binary image showing color

Kind of stuck: am converting a grey-scale image (imageUndistorted) from another part of the program, to be binarized. Where am I going wrong? The faux blob circles are correct, just not expected in the binary image.

imageUndistorted(works great from thread)
threshold(imageUndistorted, matBinaryImg, 60, 255, THRESH_BINARY);
imshow("Binary Image:", matBinaryImg);
waitKey(1);type or paste code here

see the documentation

cv::threshold accepts multiple-channel arrays and the result will be multiple-channel.