so what would you say are the 3 best colors to you for plastics.

Green pumpkin with black flakes

Black with blue flakes

Black with red flakes

I also like clear with silver glitter

8-)

Green pumpkin with black flakes

Green pumpkin with copper flakes

Watermelon with red flakes

I also like bubblegum/hot pink for smallies

I guess that really depends on what type of water you fish but here's my list

Red Shad

Watermelon

Watermelon red

tho I would definately add a white in there for flukes and trailers

Mottfia

Green Pumpkin

Black Grape

Watermelon Red

Variations of Green pumpkin, Watermelon, Black and White are definitely my main ones

1.  Green Pumpkin with Black Flake

2.  Watermelon

3.  Moccasin Blue

For cranks, shad or firetiger. 

black blue

green pumpkin

motor oil

In a general sense, black, motor oil, and some greenish brown color will cover the bases.

When it comes to actually improving your bite, its definitely lake/forage/season specific.  That takes time on the water, and my recommendations from my lakes might not align with your body of water.

Red Shad

Watermelon w/ red flake

Some variation of a rainbow trout color pattern

green pumpkin w/black flake

watermelon seed

pumpkin w/green and black flake

Odd that no one mentioned 'white'.

Bass eagerly strike chrome spoons, white-bellied topwaters and white spinnerbaits,

why would they reject a white soft-plastic grub?    (they don't)

Roger

light, dark, and in-between

any watermellon variation

junebug

craw colored

Cinnamon Pepper Neon/June Bug Laminated (Camouflage).

Junebug/Blue Tail

Black Neon Laminated

In no particular order:

Green pumpkin, grape, and black. White would be #1 for grubs.

Tom

1st three:

Watermelon/red and black flake

Black/blue flake

Green pumpkin/black flake

2nd three:

Junebug

Black/red flake

White

Watermelon w/ red flake

Black w/ blue flake

Junebug

depends what type of plastic they are... topwater frogs?

White / black / chart

senkos ...

green pumpkin, watermelon red flake, silver flake

trailers...

green pumpkin, black/blue flake, pbj

My three primaries:

Green Pumpkin

Watermelon Red

Junebug

and a very close 4th Black w/ blue flake

green pumpkin

watermelon red

Redbug

Those aren't colors, they're shades, BUT it's probably the best reply.  Specific colors are subjective to the species, the region and the conditions. 

light, dark, and in-between

Watermelon / red flake

Pearl / sliver flake

Black / blue flake

junebug shades

black and blue

old road kill camo.

1. Watermellon red flake

2. Junebug

3. Bull Frog

Zoom colors are the benchmark used here.