How do you remove red eye effect in pictures?
Most any competent computer photo editing software will have a red eye removal function. To AVOID the problem in the first place, you need to NOT have a flash blasting off directly into someones face / eyes. Either learn how to take photos with natural light to avoid flash, or use external lighting components that place the flash OFF camera.
There are plenty of apps that have filters when you take photos or edit them later. App store. You could old school and and make a home made filter.