Lenovo A6000 Custom Rom named ColorOS, based on Android Lollipop. A less popular but smooth custom ROM for Lenovo A6000 which is fast and has the options to change the themes as well. A lot of modifications has been done to meet the expectations of the Lenovo A6000 users. ColorOS custom ROM has been a successful ROM already among other devices apart from Lenovo A6000, this version was made for Lenovo K30/Lemon, and it can be used on Lenovo A6000 as well.
ColorOS for Lenovo A6000 and Plus is based on Android Lollipop 5.1.1 running on 64-bit CPU architecture which requires ARM64 Gapps. Your device must be upgraded and running on any custom ROM or stock ROM based on Android Lollipop. If you are on KitKat then please follow this guide to upgrade to Lollipop and then flash the ColorOS on your Lenovo A6000/Plus.
Apart from the native app center, you can even flash GApps to get the Play store and other Google core services. You might even consider MIUI 7 which has similar features and has more custom features or you can upgrade to Lollipop instead.
WARNING: Rooting and unlocking bootloader breaks the warranty of the phone. You are solely responsible for the loss of your dead SD card and system not booting.