I have purchased all kinds from eBay, Ikea and Amazon.
The one I got from eBay died within a few weeks. Ikea Tradfri is fine but they are just white. about $14. (But, think about where you really need color bulbs. Seriously, like why would I need one in the closet?)
I bought Seedan RGBW bulbs and seems to work well ( B09MW54DZX ), but it is currently unavailable. $24 for two.
Amazon pushes stocks Sengled bulbs, and you can get a pack of 4 now at $60. ( B07HL5GPPF )
The TP-Link Kasa bulbs are also on sale for $25 for four. ( B08TB8Z5HF )
The only thing I caution you is that saving a dollar or two on electric parts does not worth the increased risk. What I mean is big-name company, and/or UL listing does come handy if you do not want to burn your house down. I had a relay plug that I got a “great deal” on (saved like $3?) and almost set my house on fire. When I took the charred plug apart, it was put together by a drunk, blind monkey, with periodic seizures.
( the codes after the Amazon items is just their internal code so you can use amazon[.]com/dp/ to take you directly to the item ).
I have about 10 of the Wiz smart bulbs. Some tunable white, others are WRGB. All work well and have been for quite some time. Yes, they are WiFi, not Zigbee. But work well just the same. I did have some issues getting the Matter compatible bulbs to just connect like the non-Matter bulbs did, but they did eventually connect.
Also, those Amazon prices are sky high! Wow! You can get the 100 watt equivalent bulbs at Lowes for about $20 and $10 for the 60 watt WRGB ones.