Lately I've discovered that I can tell the "value" of colour better in a photograph than in store lighting. You know the case - is this tan green too dark or too light to contrast with that tan ?
I'm taking my camera now. I lay the bolts together on the store table and snap a photo. By looking at the photo, I find I'm making better choices.
This all started when I took a pic of a bargello "Ribbons in Motion" quilt that I finished. In the photo, it is obvious that I have one of the greens in the wrong place - I have a lighter one on each side of it instead of having them in order of value. It looks great anyway, but I was a bit peeved with myself.
Here are some pics so you can see what I mean.

I think it looks great!!! I love bargello but have been afraid to try it!.

Great tip - thanks!

WOW I love this quilt.

What a Beautiful Quilt, love the colors, so many small pieces

I love your Bargello quilt. I see nothing wrong with the way it turned out.

Its stunning may I ask what the name of pattern is?

I wouldn't notice it as an error in the ribbons quilt if you hadn't told me -- looks like just the way the light hits the ribbons!

Cool tip!

That's a good tip and your quilt is beautiful!!