Version 2.0.0:
Go to Settings Tab > General:
Expose the option to add an ID attribute to HTML elements - Enable
In Design Tab >
Select your Input and set its ID Attribute (at the bottom of the properties settings) >
Choose Placeholder Color element and use the value from the previous step
Live Demo:
https://placeholder-color.bubbleapps.io/version-testhttps://bubble.is/page?name=index&id=placeholder-color-----
Version 1.0.0:
1) Install the plugin :)
2) Add your custom color value (#000000)
3) Set Placeholder color to "Red" of your input
4) Take a beer and enjoy ;)