How to change placeholder color in textarea?

You can change it with ::placeholder in your CSS styles.

textarea::placeholder {
  color: red;  
}

Since some older browser may not interpret this reference correctly, in most cases I’d recommend using this instead:

You should also set the color of ::-webkit-input-placeholder, :-moz-placeholder, ::-moz-placeholder , and :-ms-input-placeholder.

<style>
    textarea::-webkit-input-placeholder {
        color: #ff0000;
    }

    textarea:-moz-placeholder {
        color: #ff0000;  
    }

    textarea::-moz-placeholder {
        color: #ff0000;  
    }

    textarea:-ms-input-placeholder {
        color: #ff0000;  
    }

    textarea::placeholder {
        color: #ff0000;  
    }
</style>

Example:

<style>
    textarea::-webkit-input-placeholder {
        color: #ff0000;
    }

    textarea:-moz-placeholder {
        color: #ff0000;  
    }

    textarea::-moz-placeholder {
        color: #ff0000;  
    }

    textarea:-ms-input-placeholder {
        color: #ff0000;  
    }

    textarea::placeholder {
        color: #ff0000;  
    }
</style>

<textarea placeholder="Textarea with red placeholder"></textarea>

Output: