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I would call that a pixelated blue screen—this looks like a hardware fault.
You give no back ground on what kind of machine you have, what macOS you are running, any back ground information in an effort to paint a bigger picture. You don't mention if it boots further or is stuck there; does it resolve?
Under the circumstances I suggest you take it in—
In or out of warranty you can get a free over the counter 'Apple Service Diagnostics' test and ask specifically for the VST (Video Systems Test)
https://www.apple.com/retail/geniusbar/
https://checkcoverage.apple.com/
https://support.apple.com/my-support
If you see a blue screen at startup
About the screens you see when your Mac starts up - Apple Support