It's been awhile since I raised a parahybana, but if this info helps, I raised a 3/4" sling to adult size in just a little over 6 months. It ate almost non-stop! So, adult coloration should happen within 5-6 months.
I agree, I got my parahybana in april (very small, under 1 inch) and it's about 4 1/2" now. Not quite the adult coloration (carapax lighter than adult, otherwise adult coloration). it's molted 5 times in my care, and it seems a molt is upcoming now.