You can easily add CSS for customizing the addons on your own.
For that, you need the create the required CSS & place it in the app’s Custom CSS setting, and save it.
You can change the font color, font style, and checkbox colors to match your store’s Theme.
Note: Edit code as required before implementing

You can use the below CSS (Update as required)
/* for addons title*/
.spice-spa-addon-product-title, .spice-spa-addon-product-title *, .spice-spa-addon-product-title .spice-spa-addon-product-link { font-family: inherit!important; font-size: 15px; line-height: 1.25; font-weight: 600; text-decoration: none; color: #000!important; }
/* for addons price*/
.spice-spa-addon-product-price { font-family: inherit!important; font-size: 14px!important; color: #000!important; }
/* for checkbox*/
span.spice-spa-addon-checkbox-text { border-color: #000; } input.spice-spa-addon-checkbox-input:checked+span.spice-spa-addon-checkbox-text { background-color: #000; }
/* for cart addons*/
.spicegems-addon-product-title { font-family: inherit!important; font-size: 15px; line-height: 1.25; font-weight: 600; text-decoration: none; color: #000!important; } .spicegems-addon-price { font-family: inherit!important; font-size: 14px!important; color: #000!important; font-weight: 600; } .sg-primary-btn{ color: #fff!important; background-color: #000!important; border-color: transparent!important; }
And if you feel stuck anytime, reach us at help@spicegems.com