If they are ceder and you want them to stay wood looking not black , i wood suggest a couple of coats of ceder seal which will help prevent discolouration, what you have already put one is a wood preserver, we are now talking wood apperience, ie colours or not
if you want to colour your hive without the paint problems i wood suggest sadolin, it is a varnish type coating but with the ability to allow the wood to breath, i personaly used it and it vast colours for years
Paintings next but to last out side we are looking for one coat primer and two to three undercoats and at lest two gloss coats all with good quality paint cheap stuff does not last, as long as it is washed every year and applied properly you should have to reapply the top coat every three to four years with a prberble 15 year life span before we would be looking at resanding and starting again
every one poo poo's painting in todays world but just remeber there are plenty of edwardian and victorian window frames left in birmingham, 100+ years ?
it is realy just preferance most bee keepers slap something one every so often some of use take pride, depends how much time you have have aswell