My one overall preference is that I like markings. I don't care for solid colored dogs aesthetically.
It depends a lot on the breed, but overall I love red dogs. Orange and liver (or whatever individual breeds call them.) It's funny because I strongly preferred black pigmentation before I got Rowan, and now I'm a sucker for the red ones.
In Brittanys, I strongly prefer orange and white piebald. I like both clear white and white with ticking. I don't particularly care for roan in either orange or liver, but I don't hate it, either. I like liver tricolors over liver and white.
In Silkens, I don't really care for extreme piebald dogs. Give me more color than just a little spot or two! I love, love, love red brindle. I think my ideal dog would be an Irish marked red brindle, although I'd be thrilled with a piebald, too. I like the other varieties of brindle that they come in, too. I'm not huge on solid cream dogs, and the potential dam of my litter is solid cream, so watch me get one just like her
My breeder has produced (so far) the only red sable watermarked dogs in the breed, and they're gorgeous. I LOVE a black mask on them, but most dogs that have them lose them as they age.
In Ibizans, I like a lot of red, either Irish marked or piebald.
In GSDs, I'm starting to really like black & red. I also love bicolors, and black & tan on some dogs is gorgeous. I don't care for sable as much as I used to, but on some dogs it's gorgeous, especially a nice rich sable, or a LH sable like Carma. I like solid black but don't prefer it like I used to.
In Standard Poodles, I really like silvers and reds (nice reds... you see a lot of iffy dogs in red just because it's popular.) I also like partis. Black, brown and apricot are all middle-of-the-road for me. I like them all but don't LOVE them. White is my least favorite, probably because solid white dogs just generally don't do anything for me.
In Aussies, I love bicolors. Black bi and red bi are my favorites, I like bi blue merle a lot, and red merle tends to be my last favorite. I actually kind of prefer a muddy blue merle over a clear blue merle. I love rich red on red tris, and black tris, too. I'm not huge on blue or red merle tris. Actually pretty much all of that goes for Koolies, too, just add on that I also love solid black and red on them.