Since you simply want to change the color of the metallic and you're working on a PNG, you could start by creating a normal silver metallic. There's many tutorials for this.
Then you could simply add a layer with your color, and choose a blending mode to colorize it. You can add a layer mask to that layer to keep your transparency. Explore the different modes, maybe there's one you'll prefer and you can also play with the transparency of that colored layer too for different effects or less saturation.
If you want to simply create your own gradient with the right color values, you can still use the blending mode suggested above to select the matching colors for your gradient; at least you'll know what colors to use and then how to customize the premade texture, if it's possible.
You can use the color picker tool in Photoshop and get the different Hex recipes to apply them to any silver effect tutorial instead of the grays.
Here's some examples:
With a layer using blending mode "Overlay"
With a layer using blending more "Color"
With a layer using blending more "Vivid Light"