Can't remember how I did this. Creating b/w object in Photoshop that can be colored in InDesign

Years ago, in an earlier incarnation of both Photoshop and InDesign, I was able to scan a hand-written piece of  "art", manipulate it in Photoshop, then import into a bounding box in InDesgin, where I can turn b/w object to any color. Years later, I've been trying to figure out what I did then, but can't. I'm trying to figure out how to to save the image in Photoshop so it can be colored later in InDesign. But, without having to color it in Photoshop before I import it to InDesign. I have the older objects, in this case, hand scribbled alphabets that are b/w white but I'm able to change them in InDesign. If this sounds at all clear, please let me know how it can be done. Maybe the steps have changed in a decade. Below is a simple example. The original letter is b/w, tranparent background and saved as grey, in Photoshop. Then brought into InDesign, it's color changed then. I can't replicate this any longer. Thanks.