As the grips are bakelite ,superglue will do the job without any need to add colour. Just don`t use too much of it , Oh and be quick, or you can get a slow acting superglue that allows you about 30 seconds to get the correct position before it sets.
If using superglue what I do is this .. remove the grip panel .. apply a light coat of oil onto the metal grip frame ( to prevent the glue from sticking to it), then refit the grip panel to the pistol but do not tighten the screw fully. Now apply the glue to one half of the join and slide the broken piece into place and hold it while it sets, then re-tighten the grip screw.
Just my two penneth anyway.
Pete.