You can override the render_buttons function

odoo.define('my_module.CustomSaveButtonName', function (require) {
    "use strict";

    var FormView = require('web.FormView');
    var core = require('web.core');
    var QWeb = core.qweb;
    var ajax = require('web.ajax');

    ajax.loadXML('/my_module/static/src/xml/button_save.xml', QWeb);
    FormView.include({
       render_buttons: function($node) {
        this.$buttons = $('<div/>');

        var $footer = this.$('footer');

        if (this.options.action_buttons !== false || this.options.footer_to_buttons && $footer.children().length === 0) {

            if(this.model == 'my.custom.model'){
                this.$buttons.append(QWeb.render("FormView.buttons", {'widget': this, 'custom_save_name': 'MyName'}));
            }else{
                this.$buttons.append(QWeb.render("FormView.buttons", {'widget': this}));
            }
        }
        if (this.options.footer_to_buttons) {
            $footer.appendTo(this.$buttons);
        }

        // Show or hide the buttons according to the view mode
        this.toggle_buttons();
        this.$buttons.on('click', '.o_form_button_create', this.on_button_create);
        this.$buttons.on('click', '.o_form_button_edit', this.on_button_edit);
        this.$buttons.on('click', '.o_form_button_save', this.on_button_save);
        this.$buttons.on('click', '.o_form_button_cancel', this.on_button_cancel);

        this.$buttons.appendTo($node);
    },
    });
});

Then in a template located in /my_module/static/src/xml/button_save.xml

<?xml version="1.0" encoding="UTF-8"?>
<templates xml:space="preserve">
<t t-extend="FormView.buttons">
<t t-jquery="button.o_form_button_save" t-operation="replace">
<button type="button" class="btn btn-primary btn-sm o_form_button_save" accesskey="s">
<span t-if="custom_save_name" t-esc="custom_save_name"/>
<span t-else="">Save</span>
</button>
</t>
</t>
</templates>
For the background color, use the same logic. The this.dataset variable contains useful information 
like the context dict.