The rhumb line from the VI to Colon will take you too close to the Columbian coast and into a rought spot that varies in intensity with the seasons. You'd be wise to check the pilot charts where you'll see the spot north of Columbia where the significant wave height is higher than elsewhere. While the exact routing will depend on the weather of the day, you may find that a rhumb line from the VI to somewhere around 13 N, 77 W and from there direct Colon will serve better.
The pilot for May is athttp://msi.nga.mil/MSISiteContent/St...106/106may.pdf
A blow up of the relevant area is below: