Not possible with JPEG. Open in Photoshop, double-click on the Background layer to create a non-background layer, and delete the surrounding background pixels to create transparency. Save as a PSD into InDesign.
@lizabys – there is another way, if the effective resolution of your scan is high enough: let's say 600 ppi and above.
Convert the JPEG to a 1-Bit (Black & White) TIF file in PhotoShop, place it in InDesign. Now the "background" is gone and you can color the placed image inside its container as you want, even white…
Downside: you'll lose all "gray" tones of the original scan.
There´s third way too: It´s possible to add clipping path to JPEG image. Only pixels inside clipping path will be visible after placing it into InDesign. So basically you can remove background of JPEG that way.
It´s a bit outdated technique, personally I prefer PSD method Steve mentioned...