Contractor is summoning the electrician to alter the light quality. Is this possible, post installation?

See what the electrician is able to do first. If you are not satisfied, work with the electrician and your contractor to resolve the problem.

No one here knows what things look like, or the specific lighting you have.

Light comes in many color temperatures. With some LED lights, you can change the color temp right in the fixture (I have some like this).

Our electrician talked to us about what color light we wanted for our undercabinet lighting. It's a shame yours didn't do the same.

See if the fixture has adjustable color temperatures (Kelvins, or K). Many fixtures now have this feature built in. If not, it sounds like what you want is a 3000K fixture.

The LED strip lighting delivers a hideous, cold light quality like for some industrial or commercial application. Contractor is summoning the electrician to alter the light quality. Is this possible, post installation? Thank you.

100% possible, as are most things with enough money.

Is this the light under your upper cabinets? If yes, it can definitely be changed.

Electricians tend to pick the cheapest/easiest choice, available that day, at their preferred electrical supply shop. Hopefully your contractor will cover some of the cost, since they did not offer you options.

The electrician probably used 4000K or 5000K LED strips. They might be an adjustable version, but can still be changed out if they aren't.

I had specified 3500K LED throughout most of my house. The electrician got the correct ones for the kitchen, but got 2700K/warmer ones for the laundry room. Don't love them, but not worth changing in the laundry room. Mine are not adjustable.

porkchop_z5b_MI is correct. Most likely, though, is that the color temperature is not adjustable so the fixture or LED strip will have to be replaced. I'd consider replacement fixtures that have an adjustable color temperature (e.g, 2700k, 3000K, 3500K, 4000K, 5000K) so you can set them to the temperature you prefer. I'd use 3000K or 3500K LED strips if you go that route. If the fixtures or LED strips are controlled by a wall-mounted dimmer, make sure the new lights are dimmable and that the dimmer supports LEDs.