The phrase "occasional flashes" refers to moments or instances when something happens suddenly or unexpectedly, but not very often or regularly. Full definition
The design of the rooms is stylish and contemporary: think a predominantly monochrome colour scheme with occasional flashes of colour (in our case turquoise and bright yellow). (thetravelmagazine.net)
During his three years in the sport, he proved a solid midfield driver who was prone to occasional flashes of brilliance, and also featured in a couple of iconic moments. (wtf1.com)
Nerve cells tower over you on all sides, pulsating in hues of blue, green, and yellow with occasional flashes of red. (newscientist.com)