If you’re looking for an affordable color smart bulb that works with both Amazon Alexa and Google Assistant, the Sylvania A19 Smart+ Full Color bulb is a fine candidate, although you can’t buy just one.
This standard A19 bulb connects directly to Wi-Fi networks, meaning there’s no need for a bridge or smart-home hub. Sylvania’s mobile app offers a variety of grouping options, lighting scenes, and powerful automation tools. That said, we still prefer the more polished apps that come bundled with our favorite A19 smart bulbs from LIFX and Philips Hue. The Sylvania bulb also lacks the HomeKit support that LIFX and Hue bulbs deliver, but that will matter only to Apple users who use that ecosystem.