Many people do something similar, notifications are a popular use of RGB W bulbs.
If you don’t want to use a bridge your best bet is either the Osram lightify RGBW or the LIFX bulb.
Personally, I would recommend the LIFX at this moment because there have been some complex technical issues regarding the Osrams not repeating when they were supposed to. This is mentioned on the official support page.
https://support.smartthings.com/hc/en-us/articles/214191863-How-to-connect-OSRAM-LIGHTIFY-Bulbs
This isn’t a problem with the LIFX because they are Wi-Fi, not zigbee, so they don’t repeat for anything anyway.
https://support.smartthings.com/hc/en-us/articles/205956530-How-to-connect-LIFX-light-bulbs