4.3(a) is usually not about your idea. It means App Review matched your binary, metadata or concept to other submissions, and the rejection rarely says which ones. Adding features doesn't change that match, which is why you got the same result. What tends to work:
Check where the code came from. If any part of the app started from a template, tutorial or open-source sample that many other apps also used, that's the most common trigger. Rewrite or remove that part, not just the UI.
Make the metadata clearly yours: name, subtitle, icon, screenshots and description should not look like other color-identification apps. Lead with what's unique (the colorblindness simulator for family and friends).
Ask before resubmitting. Reply in App Review and ask which part of the app or metadata is considered similar, and say it's your own code under a single bundle ID. You can also appeal to the App Review Board with the same explanation and a short screen recording of the simulator feature.
Avoid quick resubmissions with small changes. That pattern is what puts accounts at risk. One substantive change with a clear reply, or an appeal, is safer than several quick tries.
Topic:
App Store Distribution & Marketing
SubTopic:
App Review
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