Akro - have a read of this for your intervals.
http://www.casa.gov.au/ADFiles/equip/emy/EMY-002.pdf
Colour - well if you don't like black don't buy one, if it doesnt bother you then so be it. Our pax wear them for up to 2 hrs, the crew jackets, Mk44, (exposed to extra sun light etc) are a very dark blue, again no complaints and we fly and operate all the way up the northwest coast.
For alternate colours your choice is fairly limited
Constant Wear Lifejacket SMA2158 | www.safetymarineaust.com.au