http://led.linear1.org/led.wizSuggest you add this site to your favourites list......even gives you the colour codes for the correct resistors.
Maplins, Rapid Electronics,RS, all useful suppliers and quote the If (Forward Current) in mA (milliAmps) V max (Maximum voltage required by the LED. and you know Vf (Supply Voltage of your boat)
Just enter those facts and the number of leds you want to use on the above site.
Suggest you do separate calculations for Red/White/Green/Blue/Orange....as they all have different characteristics.
Have fun
hth
Rex