Red/ blue is nice. I have a good source locally for 3/8" PEX and fittings and it is MUCH easier to work with than 1/2" PEX. Either way STRAIGHT lengths are far easier to work with than coils. I prefer the Watts/SeaTech plastic fittings as they don't corrode and look like crap three weeks after you completed the job.
Building this manifold too literally two or three minutes...
You don't need to pay "marine" prices. Watts owns Seatech and sells the identical fittings under the Watts brand... I pay about 35% less through my local plumbing wholesaler...
Please be very careful that you are buying either all metric or all US pipe size. Early on they forced metric PEX & fittings into the marine market so they could charge us boat loads of money for "proprietary" marine PEX and fittings. A lot of the metric PEX is still out there and it will not mix with US sized PEX.