Bought some of the fading watermelon red senkos on tackle warehouse. What type of water clarity should I throw these in? Would they work in stained water? The color on these worms are kinda dark for watermelon lol 

The clearer the better for any color of senko.  It is the action of the bait that separates it from all the other stick worms and attracts fish.

I fish a lot of slightly stained water and do well with senkos. That color is dark enough yet natural enough to work in a lot of water conditions. I wouldn't throw it in Crystal clear or mud...anything in between is fair game.

That color can work anywhere though I prefer fairly clear water and sunshine.  That is my go to color when pb&j is slow.

I tend to think of watermelon as a bit lighter and more transparent in comparison to  Yamamoto color standard.  This color does work in many situations.  However, I have a local quarry lake that is gin clear where the fish favor transparent colors.  Baby bass color it is for that lake.

WM Red : Best for clear water , sunshine and around grass as the red flake provides a little contrast to the grass. If no vegetation present I tend to use Green Pumpkin more in those situations .

I use those in ponds. The top 6"-8" of water is relatively clear but becomes more stained with algae the deeper it gets. That color Senko is very effective.

Behind black w/blue flake, that color is my #2 producer. I throw it in everything from chocolate milk to drinking water.

That one has been the best for me in all water colors. 

Everybody is going to say clear water, and they're not wrong -- as a natural color, any kind of watermelon is a good choice for clear water.

 

But consider the red flake:  In clear water, red doesn't penetrate as deeply as other colors of the spectrum, fading to black around 20-25 feet (in many freshwater environments if you are viewing from a few feet away).  In heavily-stained (especially brownish) or muddy water, red light is actually the least absorbed, and penetrates the best of the spectrum. That is, while no part of the spectrum penetrates as much as it does in clear water, red ends up penetrating the best as the other colors get absorbed more, giving red better visibility than other colors when muddy.

 

Flake colors generally benefit from brightness, as the flakes shine and glint as they catch the sun. 

So: GIve Watermelon-Red a try in heavily stained or muddy water, on a bright day.

Watermelon red is a killer color for any soft plastic lure.