What is the rule for wearing tropical blue during travel ?

Auxiliarist's traveling on "Coast Guard" orders (either written or verbal, re-imburseable or not) may wear any appropriate uniform/authorized uniform of the day for the region area traveling from/to with the exception of the ODU.

Caveat, the ODU maybe worn while traveling to and from a duty station.  It is not a "Liberty Uniform".

Auxiliarist's traveling on "Coast Guard Auxiliary Association" orders may not wear their uniform while traveling.