In automations
Drop down for device
Then blink
dropdown for speed of blink
dropdown for duration if zero continuous
later could add colors 
Check the effects available for your device.
e.g. for Lifx: https://www.home-assistant.io/integrations/lifx/#light-effects
‘Blink’ is not an inherent capability of all lights and switches. In fact, very few implement it.
The old-school way of making lights blink is to transmit a continuous stream of on/off commands, spaced about 1 second apart. For anyone with a large installation of Zigbee or Z-Wave lights and switches, this technique will flood their mesh networks with commands and acknowledgements. It’s an inefficient way of blinking many lights.
Alternately, you can use Zigbee groups (also known as scenes in other lighting technologies) to efficiently (with a single command) turn many lights on/off. However, if you have a mix of lighting technologies, including some that don’t support groups/scenes, then it becomes inefficient again.
In addition, Home Assistant does not automatically optimize lighting commands. It is unaware that you may have, for example, existing Zigbee groups so it will default to turning each individual light on/off as opposed to turning a Zigbee group on/off.
So the request for a feature to “Then blink” is an enormous challenge to implement efficiently. Plus it has to translate into a workable automation and, frankly, that’s light-years beyond what the Automation Editor is currently capable of achieving.
OK thanks, I did not know anything about “flooding” the network with commands. I suppose I could find some time of flasher for the bulb(s) and just set them to on and have the flasher do the lifting
Imagine this is the stream of commands to a single light and the acknowledgements from the light that it received the command:
ON - ACK -- OFF - ACK -- ON - ACK -- OFF - ACK -- ON - ACK -- OFF - ACK -- ON - ACK -- OFF - ACK --
Now multiply that stream by number of lights you want to blink. Let’s say there are 10 lights. So we begin with 10 ON commands, followed by 10 acknowledgements, etc. The ten ON commands are not generated simultaneously (fractions of a second apart), so some lights will turn on slightly later than others, so the 10 acknowledgements will also be transmitted slightly skewed. Therefore some lights will be turn OFF before others and so on and so on. Clearly, there will be a lot happening on the mesh network and the end-result is not 10 lights turning on/off simultaneously but in a skewed manner (sometimes referred to as the ‘popcorn’ effect).
AND the skew will not remain constant, it will (continuously) migrate across the lights, so if will look more like a naff prop from a 1950’s sci-fi movie