Engine runs hot Blue Particles in Coolant

[CamelotShadow]

Just got a thermo installed
old was sticking
Engine still ran hot getting to about 110 115
not as bad as the 120 redline before repair

Coolant level was down 6 pints which I added today
Shop said it might have had an air pocket when they filled it.

Hoping thats it

Haven't started it yet
The coolant in the resovoir had blue/green particles floating in it after I added water.

Is this normal?
Is it bad?

Should I have the coolant changed
I got the car w no records but my guess was the coolant is 2 to 4 years old which I told the shop but it only has about 300 miles on it.

The radiator is a Behr so I think it is not original but it has a benz star om it.

Started up right away
Only my 4th start
Idle was a bit hi over 1000
Oil pressure 3
I ran it about 15 min in Park
idel went down to about 800
Temp went up to about 80
T stat opened about there as top rad hose got warm
Temp went up eventually to around 100 oil pressure 3

I shut it down

One thing I noticed is that the res coolant tank stayed cold
It never entered the system
Is this normal?
I was hot yesterday when it was about half filled.

Thanks