I used Evergreen for the sheeting and a darker Melchers Green for trim and soffits. It blends well in my wooded setting. I have also seen grey with green trim, which looks quite nice.
I've seen some nice combo's but it's really a personal choice. I like 2 shades (light & darker) of a grey, red with white corners & trim has a trad."AG" look, my current bldg. has a "clay" color for the trim & doors with lighter version for the siding. Take a look at http://www.bing.com/images/search?q=morton+buildings&FORM=HDRSC2
I like to use a plain galv. roof, it "mellow's" from being bright & shiney (new) in a short time to a dull non color and kinda "go's away" and is no longer an issue of conflicting with what you may choose for wall & trim colors. Disreguard if you are using shingles, but that color needs to be a consideration also.
