What is colon : in npm script names?

I believe it's just a naming convention to group a set of related tasks. For example you might have

"test:ci": ..."test:units": ...."test:integration"...

In this case it is grouping a related set of test tasks.

It would be down to the package author to specify. You can split tasks out like described in the answer above and then have a 'global' test command which combines each of them e.g. test:ci && test:unit && test:integration enabling you to run them all at once or when individually when needed.

You can use npm-run-all (link) and use the command npm-run-all test:*, which would then find all scripts starting with the test: group.

I solved this by running - "npm run <scriptName>"

Within my package.json file, I had two "start scripts"

start: nodemon server.js

start:elasticsearch: docker run elasticsearch..

Solved with npm run start:elasticsearch

If using Yarn package manager, you can use a colon in the name to call the script from any workspace.

According to the yarn docs on How to share scripts between workspaces?:

Little-known Yarn feature: any script with a colon in its name (build:foo) can be called from any workspace.

Also, according to yarn docs on CLI > run:

Otherwise, if the specified name contains a colon character and if one of the workspaces in the project contains exactly one script with a matching name, then this script will get executed.