Most smart light bulbs do a good job of being clear about the platforms they support by putting little "Works with" badges on the packaging. If you're an Apple HomeKit user, for instance, then look for bulbs that have the "Works with Apple HomeKit" badge on the box. Easy, right?
Well, not really. The problem? Some bulbs require hubs to work with certain platforms, but not others. For instance, the first-gen C by GE LED can connect directly with Google Home speakers and use them as a hub for control outside of Bluetooth range, but if you want to connect with Alexa, then you'll need the C-Reach plug-in hub, a separate $50 accessory. The second-gen C by GE Direct Connect LEDs are a little better -- they still connect great with Google, and now, you don't need a hub to pair them with Alexa, either.
I've done my best to make those connection requirements clear in that comparison chart a few sections up, but here's a quick breakdown by platform:
Pretty much everything works with Alexa at this point, so you've got lots of options. If you have a fourth generation Amazon Echo speaker (or a separate Zigbee hub), then take advantage of that speaker's Zigbee radio by going with Zigbee smart bulbs like the Philips Hue White LED, the Sengled LED, or the EcoSmart LED. The new Echo can control all of them. Same goes for other Echo devices with a built-in Zigbee radio, including the second-gen Echo Show" target="_blank, the Echo Show 10" target="_blank and older Echo Plus" target="_blank.
If you don't have one of those devices and you don't want to buy one, then go with a Wi-Fi bulb from Wyze, Philips Wiz, Cree Lighting, Lifx, Eufy or TP-Link. Of them, I'd go with Wyze for the extra brightness or Lifx for its best-in-class app and its excellent IFTTT channel.
The full color version of the Lifx Mini boasts the best-looking colors of any bulb in this price range, but it costs $35. If you want Alexa-compatible colors for less than $20, go with Philips Wiz or a Cree Connected Max bulb.
Like Alexa, Google Assistant works with almost every major smart light on the market, so again, you've got a lot of options. Even so, I think C by GE LEDs are an easy standout here. The direct Wi-Fi connection with a Google Home smart speaker is easy to install and speedy in action, and the bulbs themselves offer lots of quality, too.
The new, second-gen, "Direct Connect" versions of the bulbs work well with Alexa, too -- but you probably don't care too much about that, so it's fine to stick with the first-gen versions, especially since it'll be a lot easier to find them on sale.