GIMP - RGB image colours not working

[mholder]

(09-30-2018, 12:13 PM)Monica Wrote: The colour menu greyed out was a red herring - that's just because the layers were in groups. I still cannot change any colours at all though despite image mode being RGB
The file is here:
http://www.filedropper.com/savethedate_1

Colorize also works
   
Just curious, why is this in 32 bit?  I think internally GEGL is 16 float.  I am no expert, but I wonder why 32.