I have been using ColorNote since I started using Android devices 4 years ago. ColorNote is a simple note-taking tool that is very popular. Like a notepad, you can tag each note with a colour code. My favourite feature is the ability to add widgets that look like notepads to the homescreen. You can also sync all your notes across your Android devices when you backup online which uses AES encryption standard.
I use ColorNote primarily to create disposable task lists which I do not need to keep, as opposed to other note-taking apps like Evernote where you keep track and store long-term information. It does not take up much space – only less than 1MB to install – making ColorNote a great app for your smartphone.