Hi,

I have create a random number between 0-1 for points and I'm using this number with color node and ramp to generate some specify colors. Because the point qty is not fixed, this random number start to change over the time and of course color as well. How can I lock the random number for point so it doesn't change after it is generated?

if your point numbers are changing, base Attrib Randomize on some attribute that is stable and doesn't change, if you don't have one it's up to you to create one by any means possible
for particle sims it is usually id attribute, that is generated during sim
you can specify such attribute in Attrib Randomize/Options/Seed Attribute

I think I understand from where problem comes but let me explain my setup. I have a grain simulation (2 million particles) and I import it in my instance network. I have 90% non visible particles so I delete those based on geometry. After this I up-resize left particles 10x. This cause the problem where my random not work anymore. It works if up-resize first and then randomize and delete but this takes 10x times longer in every frame because I up-resize non-visible particles so much.