Google used to use small green bars to display the competitiveness of keywords.

Now the Google tool is only showing text based descriptions of competitiveness - Low, Medium or High:

The new competitive labeling is as follows:

• Low - Competitiveness number under .33
• Medium - Competitiveness number between .33 and .66
• High - Competitiveness number over .67

The rating is only for adwords competition and not general search.