Shiny Omanyte in Pokemon GO will be appearing with slightly more frequency thanks to the Mega September event celebrating the launch of Mega Evolution. Omanyte will be appearing more during the the first week, Sept. 1-7 along with the newly patched in shiny Lotad. Players looking to acquire a shiny Omanyte should try to seize this opportunity.
Shiny Omanyte Pokemon GO: How to Catch
Shiny Omanyte can be differentiated from its standard form by its lavender body. Omastar is the same, with a lavender body and yellow shell.
Omanyte will be spawning more frequently in the wild due to Mega September, but you can increase your chances further by going out in rainy or partly cloudy weather, during which spawns of Water and Rock types respectively will be more frequent.
This will help get the numbers on your side to increase the chances of a shiny spawn. Also try to look for Omanyte in raids whenever you can. Raid battle Pokemon have a slightly higher than normal chance of being shiny so if you see one be sure to get out that battle pass. Omanyte appears in one star raids so if you find one it shouldn't be too difficult to defeat.