Freedom of Expression?

Remember when we were kids, and coloring in coloring books was fun? That's basically what painting is.....coloring. Only instead of using crayons in a coloring book, paints and paintbrushes are used.

At the moment, I'm laboring over a portrait commission. What I'm trying to remember is the freedom in youth of coloring in a coloring book. Back then, it didn't matter if a tree had purple leaves and a yellow trunk. It didn't matter if the sky was magenta. And it didn't matter if the puppy was green. The fun was in the expression and experimentation and the endless choice of colors, especially if one had access to a 64 count box of Crayola crayons.

It seems to me that it might matter to a client, however, who perhaps expects to have "normal" looking skin tones, dress, and hair. Or maybe it doesn't. Didn't they hire me to be the artist? Do I have complete freedom to create a unique work of art? Or am I morally obligated to stay true to more realistic parameters?

When they commissioned me, I mentioned that the representation was not going to be an exact match to real life...that given the wallet sized old black and white photograph to use as reference, that I was likely to take great liberties with color in the finished painting....and they said with raised eyebrows and a shrug of the shoulders, "Well, you're the artist..." But does that REALLY mean that I have complete freedom to paint this portrait any way I like?