Widget for rating how well users remember a word

In my app users should be able to rate how much they "know" a word, meaning how much they can recall it's meaning.

My other related question: Hanging panel after user Click

Given that, there's also a color scheme on the text itself:

  • Blue means new word
  • Strong yellow means just started learning it
  • Light yellow means almost know it
  • No color means learned or ignored (there's a small green/red underline to distinguish them)

There are 4 levels of learning (yellow shades). When a word is clicked on the text, the widget just shows up with the current status of that word selected:

enter image description here

How can I make this more intuitive? There's a color problem here: on the text yellow is used to mark unknown words, but on the status panel I want to show the notion of progress to the user, so the yellow --> white scheme doesn't work there. Any suggestions? Thank you!

Edit: Something I came up with, please eval. enter image description here

Note: Users will encounter the same word again and again. The goal is to gradually learn words, giving the constant reminder of their status.

Tags: