There are so many colors and combinations out there today.  I listed the primary colors that are mainly sold.  I typically gravitate to green / watermelon and purple.  

purple 7 inch power worm is my 1st choice.

Black, pumpkinseed, watermelon, blue fleck and others, they're all good. I suppose if I had to be limited to one color, I'd probably take black, but I really have no reason to think that it would do better than others. But it was my first color and I probably feel more comfortable with it.

Red Shad

Blue Fleck

Green Pumpkin

Watermelon Seed

Green Pumpkin, Watermelon and Black will catch fish anywhere, anytime.

But who can truly limit themselves to just three colors?  

Brad

Watermelon and pumpkin families.

watermelon and purple

That was a hard choice because Green just edged out Purple for me and I still get a lot of sucess with Manns Jelly worms in Marmalade(MOTOR OIL)

In the Yum Line I like Junebug and Smoke Pearl Laminate

In the GYCB I like 021 Black with Blue Flake and 927 Smoke Pearl Blue Laminate and 297 Green Pumpkin black flake and, and, and, and,,,,,,,,,,,,,,

In the Zoom line I like Watermelon Red

Electric grape power worms are my favorites. Green pumpkin w/red flake stick baits are a close second.

Mine is a Red Shad 7 inch power worm

My favorite color worm is Red Shad.

JT Bagwell

There's no "1" worm color that's best for all water depths and water clarities.

While you might select 'Black Neon' for working the bottom in murky water,

you might choose 'Bubblegum' for a topwater worm in clear water.

Alternatively, you could compromise using a bicolored worm with a dark and light hue.

Roger

green pumpkin works everywhere.

I noticed you didn't list Junebug -- but that may not be a primary color and may be included under purple -- if so, put me down for that.

I like purple/grape to start with. If that doesn't produce I'll move on to green or pumpkin colored plastics.

I have billions of pounds of plastics......just about every style you can imagine, but the color selection is simple.

Green Pumpkin

Watermelon seed

Pumpkinseed

Watermelon/redflake

Junebug

Red shad

Black.

White

The only baits that stray from this list are zoom trick worms.....I use the colors listd above plus bubble gum, and the zoom super fluke in baby bass. Each year though it seems I add a new "basic color"

I use watermelon colors the most, my favorites are watermelon/red and watermelon/gold.

I try to stick with natural colors as much as possible

I prefer dark colors

I prefer the green or brown colors such as green pumpkin

i like green with brown all most the same, i love a pink worm for fishing it on top floating 6 inches under the water though

I am most confident with junebug and guess thats why I feel like I catch more with it but I also like black

either watermelon or a brownish color (brown mainly for grubs)