Blue alert disable

Here you go. It's not Apple, it's FEMA that categorizes the alerts:

• Amber: AMBER is an acronym for "America's Missing Broadcast Emergency Response," which uses EAS to send vital details of very recent child abduction cases. These details could include a name or description of the abducted child, name or description of the abductor, license plate or description of the vehicle that child was last seen in, and more. In some cases, they could include a photo of the abductee, abductor, or car. These alerts are sent out as soon as possible to aid in recovering a missing or kidnapped child. Amber Alerts aren't just for children either — they can be sent out for any person's disappearance. And some lawmakers are trying to also include hit-and-runs in Amber Alerts.
• Emergency: These alerts are for things considered imminent threats. The most frequent ones are for extreme weather conditions and life-threatening natural disasters, such as tornadoes, hurricanes, monsoons, earthquakes, wildfires, volcano eruptions, lightning storms, tsunamis, mudslides, extreme heat, and considerable or catastrophic flash floods. You'll also see these alerts used for human-made disasters, active shooters, and terrorist attacks.
• Public Safety: These less-severe alerts are for threats that are not considered to cause imminent danger or for threats that occur after an imminent threat has happened. Examples include "shelter in place" advisories and "boil water" warnings. States and local governments are even using public safety alerts to issue important coronavirus pandemic messages, such as when high surges of COVID-19 cases happen in a specific area and where you could get tested.
• Presidential: Out of all of the alerts listed, presidential alerts are the only ones you can never turn off and the ones most likely to be sent out on a national level instead of regionally. These alerts are issued by the President of the United States or a designee and are strictly for nationwide emergency events, such as a national terrorist attack or nuclear invasion.
• Test: Government agencies and officials only use these alerts to check the functionality of any of the above types of alerts. These are opt-out, which you'll see below.

Here's everything Apple publishes: https://support.apple.com/en-us/HT202743

There is no such thing as a "blue alert" under the defined emergency alert system.

They simply don't exist.

If the State of Texas is abusing the alert system, that's something that should be taken up with the FCC.

P.S. Any alert will also have a heading with the type of alert. There are certainly some jurisdictions that go overboard with alerts, and people do complain to FEMA and the FCC about the quantity of alerts and the perceived severity of what instituted the alert.

I've never heard of a blue alert (whatever it is, we don't use it where I live). When you receive an alert the kind is also displayed as part of the header message -- The notification states the category of alert. So, you may have to wait for one to happen again, or simply turn them all off. But, whomever is initiating the alert may also change the category, so.....