Change Ripple Color on click of Material UI <Button />

Here is the hack for Material-UI 4.9.10

Add a class to button and then add the below code to given class

 Btn:{
    "& .MuiTouchRipple-root span":{
      backgroundColor: 'red!important',
      opacity: .3,
    },
},

Here's an example showing how to modify the button ripple for v4 (v5 example further down):

import React from "react";
import { withStyles } from "@material-ui/core/styles";
import Button from "@material-ui/core/Button";

const styles = theme => ({
  button: {
    backgroundColor: "green",
    "&:hover": {
      backgroundColor: "red"
    }
  },
  child: {
    backgroundColor: "blue"
  },
  rippleVisible: {
    opacity: 0.5,
    animation: `$enter 550ms ${theme.transitions.easing.easeInOut}`
  },
  "@keyframes enter": {
    "0%": {
      transform: "scale(0)",
      opacity: 0.1
    },
    "100%": {
      transform: "scale(1)",
      opacity: 0.5
    }
  }
});

function MyButton({ classes, ...other }) {
  const { button: buttonClass, ...rippleClasses } = classes;
  return (
    <Button
      TouchRippleProps={{ classes: rippleClasses }}
      className={buttonClass}
      {...other}
    />
  );
}

export default withStyles(styles)(MyButton);

The default opacity of the ripple is 0.3. In the example I have increased this to 0.5 to make it easier to verify that the ripple is blue. Since the button background is red (due to the hover styling), the result is purple. You'll get a different overall effect if you move to the button via the keyboard since the blue will be layered on top of the button's green background.

You'll find some additional background in my answer here: How to set MuiButton text and active color

The main resource for the styling of the ripple is its source code: https://github.com/mui-org/material-ui/blob/v4.10.2/packages/material-ui/src/ButtonBase/TouchRipple.js

JSS keyframes documentation: https://cssinjs.org/jss-syntax/?v=v10.3.0#keyframes-animation

---

Here's a similar example for MUI v5:

import { styled } from "@mui/material/styles";
import Button from "@mui/material/Button";
import { keyframes } from "@emotion/react";

const enterKeyframe = keyframes`
  0% {
    transform: scale(0);
    opacity: 0.1;
  }
  100% {
    transform: scale(1);
    opacity: 0.5;
  }
`;
const StyledButton = styled(Button)`
  background-color: green;
  &:hover {
    background-color: red;
  }
  && .MuiTouchRipple-child {
    background-color: blue;
  }
  && .MuiTouchRipple-rippleVisible {
    opacity: 0.5;
    animation-name: ${enterKeyframe};
    animation-duration: 550ms;
    animation-timing-function: ${({ theme }) =>
      theme.transitions.easing.easeInOut};
  }
`;
export default StyledButton;

v5 TouchRipple source code: https://github.com/mui/material-ui/blob/v5.4.0/packages/mui-material/src/ButtonBase/TouchRipple.js#L92

Emotion keyframes documentation: https://emotion.sh/docs/keyframes

Answer demonstrating use of keyframes: How to apply custom animation effect @keyframes in MUI?