Ok, let me try this. Normally a hurricane degenerates into a tropical storm and a tropical storm degenerates into a tropical depression at the end of the storm's life cycle as a tropical entity. The last bulletin on Alex said "Tropical Depression Alex..." and ditto for Bonnie:

"ZCZC MIATCPAT3 ALL
TTAA00 KNHC DDHHMM
BULLETIN
TROPICAL DEPRESSION BONNIE ADVISORY NUMBER 10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032010
400 PM CDT SAT JUL 24 2010

...BONNIE DEGENERATES INTO A DISORGANIZED AREA OF LOW PRESSURE..."

Note that on the last bulletin it is still called Tropical Depression. With Colin, the system went directly from a Tropical Storm to an open wave (no wind with a westerly component in this case). It is now really a gale (low pressure) center with winds still at 40mph sustained and therefore an area of tropical storm force winds still exist (as noted in the bulletins). Because Colin went directly from TS to open wave the final bulletin carried the Tropical Storm designation rather than Tropical Depression (because the wind speed in a portion of the storm is still above tropical depression strength). The status (TD or TS or Hurricane) and system name are just carried for reference purposes on the last bulletin. When a Hurricane hits far northern latitudes and becomes Extratropical, it is still called a Hurricane on the final bulletin:

"ZCZC MIATCPAT3 ALL
TTAA00 KNHC DDHHMM
BULLETIN
HURRICANE IRENE ADVISORY NUMBER 24
NATIONAL WEATHER SERVICE MIAMI FL
11 PM AST MON OCT 18 1999

...IRENE BECOMING EXTRATROPICAL AS IT RACES ACROSS THE FAR NORTH
ATLANTIC OCEAN..."

Hopes this helps to clarify the issue.
ED