- Launch Google Play Store on your device;
- Tap Menu, then Subscriptions;
- Tap the Color By Number subscription;
- In Color by Number's page, tap Cancel Subscription and once again in the confirmation box.
- Access Settings in your device;
- Scroll down and tap "iTunes & App Store";
- Tap your Apple ID (your e-mail), then tap "View Apple ID" and enter your password;
- Now, tap on Subscriptions and select Color By Number;
- Tap on Cancel Subscription in the bottom and that's it!
For more information, click here: https://support.apple.com/en-us/HT202039.
If you don't see the options mentioned in the instructions above, please ensure you are logged in with the same Apple ID/Google Account being charged for the subscription. Please contact Apple or Google support for further assistance.