Personally, I only use bulbs with good safety certifications, so I don’t typically consider the cheapest brands. (Yes, exploding lightbulbs is a thing.)
ZIGBEE BULBS: REQUIRE A SMARTTHINGS/AEOTEC HUB*
If you have an ST hub, Zigbee bulbs are probably the most popular. There are several good brands. You will also need a hub to connect something via matter.
My own medium-priced RGBW favourite is Innr Zigbee bulbs. Good brightness, ETL certified, work out of the box with SmartThings, available at Amazon in multiple regions. They are typically sold in a two pack, so check the description to validate the price.
UK:
https://www.amazon.co.uk/Innr-Equivalent-WRB-785-C-2/dp/B08FMRTV51/
US:
https://www.amazon.com/Philips-SmartThings-Required-Dimmable-Equivalent/dp/B08428JSDZ/
I like IKEA Tradfri bulbs bought from IKEA for plain white bulbs. Excellent price, available in many regions. A few community members have had some difficulty with them, but most people seem to find they work fine. They do make RGB bulbs in some markets, but lots of reports of hissing with those, which may be why they’re not more widely available.
Sengled and Sylvania Are also popular Zigbee brands in the community, but may require custom code.
WIFI BULBS
If you don’t have a SmartThings hub, then Wi-Fi bulbs are usually the best choice. Some people with an ST hub use matter over Wi-Fi.
I hear good things about Philips Wiz (a sister brand to Philips Hue, but much less expensive), but I haven’t tried them myself because I generally don’t use Wi-Fi for lightbulbs. The newer wiz models are using matter over Wi-Fi, which is nice, so if you’re using them with a SmartThings hub, you don’t need the hue bridge.
https://www.amazon.co.uk/WiZ-Colour-Smart-Light-2-Pack/dp/B0C7D47CQZ/
Depending on the country you are in, there will be quite a few other options as well, but I think these are probably the most popular in early 2024.
Tapo and Linkind are both budget brands that also offer RGB matter over Wi-Fi bulbs, but both have a higher than normal number of complaints about incompatibility and buzzing/flickering, so I think they may need a little work yet.