Certainly! To change the color of the footer text to white, you can update the `color` property in the `footer` CSS rule. Here's the modified CSS:

```css
body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #f0f0f0;
}

.container {
    text-align: center;
    background-color: #ffffff;
    padding: 30px;
    border-radius: 10px;
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.1);
    max-width: 400px;
    width: 100%;
    margin: auto;
}

h1 {
    color: #333;
}

label {
    display: block;
    margin-bottom: 10px;
    font-size: 16px;
    color: #555;
}

input {
    width: 100%;
    padding: 10px;
    margin-bottom: 20px;
    box-sizing: border-box;
    border: 1px solid #ccc;
    border-radius: 5px;
    font-size: 16px;
}

button {
    background-color: #4CAF50;
    color: white;
    padding: 12px 20px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 16px;
}

button:hover {
    background-color: #45a049;
}

p {
    font-size: 18px;
    margin-top: 20px;
    color: #333;
}

footer {
    position: fixed;
    bottom: 0;
    width: 100%;
    background-color: #333;
    color: #fff; /* Change color to white */
    text-align: center;
    padding: 10px;
}
```

Now the footer text will appear in white. Feel free to adjust any other styles as needed.