The band colors and resistance levels had changed about 2012 when we had introduced a new 3lb. band. When the new 3lb resistance level was added, we shifted all the colors down 1 level. Here is a list that gives the levels and colors of the old resistance band levels and the new resistance band levels.
Old Bands / New Bands
NA / 3 lb Yellow
5 lb - Yellow / 5 lb - Green
7 lb - Green / 8 lb - Red
13 lb - Red / 13 lb - Blue
19 lb - Blue / 19 lb - Black
23 lb - Black / 23 lb - Purple
30 lb - Orange / 30 lb - Orange
Some older bands that have the gold clip could be either the old resistance levels or the new resistance levels as this change was made while the bands had gold clips. We switched to silver clips about 2014 and all silver clip bands are the new resistance levels.