Board Thread:Questions and Answers/@comment-99.199.15.5-20160327174930/@comment-25968376-20160328105527

Silver is levels 40-49 and gold 50-59 IIRC. 60-69 is one shade of rainbow color and 70-80 a more purple one.

And although it's a visual thing, you do get a 1% score bonus up to level 50, then 1% for level 60 and one for 70. So in total you can currently get a 52% score bonus.