I know all have advised you to use stain...I would say to use transparent stain if you must...if you use a solid stain you are in for continuing maintenance and restaining over the years....I once asked a painter about all of the old tenant farmer houses here in the South all gray and how they are still standing after 100 yrs. or more...He said , they never painted the houses...wood has enzymes and once you apply a solid stain or paint to the surface the enzymes react with it and moisture gets behind the paint or stain and rot occurs....when nothing is applied the wood just weathers and does not rot....I have found that to be true on the back of one of my barns...it was sided with t-111 and that was over 20 yrs. ago....not painted or stained and it is a nice dark gray right now...the other sides that were stained with solid stain have had to be stained many times since then....Just for what it's worth.