That is an unusual color combo. To me it has a dayglo quality to it, unless of course the colors are not reproducing on my monitor correctly. from here it looks like a yellow with a bit of a green under tone.
The "made in hong kong" would indicate 60s or after, whereas "handmade in hong kong" would be more 50s, so you are in the right direction on the date. I just have never seen anything like it.
If its 60s, I would be leaning towards late 60s due to the colors but it could be running a little later than that.
Anyone else have input?