Not all bulbs support flash. Hue do of course, but not with the HE Hue Integration driver, but you can flash Hue lights with the Hue B Smart driver and app that was recently ported to HE. I have not tried this myself but sounds like it's working just fine. There's no instructions in @xap 's repo, so if you take a look at the original SmartThings post, you can understand how it works and how it should be installed (roughly).
Since it sounds like you didn't have SmartThings before HE, so take those instructions and replace the terminology "DTH" with Driver, "IDE" with hub (because drivers and apps are local here of course) and "CoRE" with Rule Machine (because webCoRE or CoRE as it used to be called is not a good idea on Hubitat. Stick with Rule Machine).
