Lightweight CSS rules for delivering a form via Gravity Forms that looks halfway decent.

asu-gravity-forms.css

// Substitute your own ID for the form that you want to style.
// Working example is here: https://faculty-resources.engineering.asu.edu/ Workshop page.


#gform_wrapper_1 {
    background-color:#e0e0e0;
    padding:2em;
    color:#000000;
}

#gform_1 .gform_title {
    background-color:#222222;
    color:#ffc627;
    font-weight:700;
    font-size:2rem;
    padding:5px 10px;
    margin:-10px 0  0 -50px;
}

#gform_1 .percentbar_blue {
    background-color: #8c1d40;
}

#gform_1 .gfield {
    padding:.75em 0 1.5em 0;
    border-bottom:1px solid #f0f0f0
}

#gform_1 .gform_button,
#gform_1 .gform_next_button,
#gform_1 .gform_previous_button {
    background-color:#8c1d40;
    color:#ffffff;
    font-weight:700;
    border-radius:5px;
    padding:10px 15px;
    font-size:20px;
}

#gform_1 .validation_error {
    background-color:#8c1d40;
    color:#ffffff;
    font-weight:700;
}

#gform_1 .gfield_error {
    background-color:#ffc627;
}

#gform_1 li.gfield.gfield_error {
    background-color:rgba(255,198,39,.25);
    color:#8c1d40;
    border-top: 2px solid #ffc677;
    border-bottom: 2px solid #ffc677;
}

#gform_1 li.gfield.gfield_error .gfield_description.validation_message {
    background-color: #222222;
    color: #8c1d40;
    font-weight: 700;
    color: #ffffff;
    font-size: 16px;
    display: block;
    margin-left: -10px;
    margin-top: 20px;
    width: fit-content;
    padding: 10px;
}

Updated again to include a maroon-ish progress bar and styled buttons for multi-page forms.