Small butt connectors. I used the same bi-color light in our
boat, each has a switch for white-off-red. Your main switch (circuit breaker?) can be left on and each controlled by its own switch. Unless you have a bunch of glue heat shrink connectors in that size, just use regular. (Dk Blue, if I
recall correctly.) If you want the
water tightness of a glued heat-shrink then use liquid tape or some caulk in the ends but if you have THAT much
water in your light you have other problems...
The
cheap crimper in most tool kits works good for these, but a good pair is worth it if you need to do other more critical connectors. Maybe it is a chance to start that tool box of quality tools you'll eventually need...