Just looks like perennial ryegrass to me. Of your seed blend, it is the fastest species to germinate, followed by the creeping fescue and tailed by the KBG, which can take up to 30 days.

Commercially packaged lawn seeds will have a label on them that outlines what they contain and in what percentages. They will also disclose the percentage of potential weed seeds. This is a US requirement but would expect CA to have similar laws. As it is virtually impossible to be 100% weed free, the estimated percentage of weed seeds disclosed should remain right around 0.01%....petty darn low, all things considered. Cheaper brands will often have higher percentages.

Of course, keep in mind that 0.01% is still about 10 seeds per thousand square foot, and that's just what went down from the bag. And trust me, for some reason, even if the grass seed does not germinate, somehow every one of those 10 seeds will manage. Ask me how I know...

Your soil had a seed bank in it from what was already there, and what blew in during the process and germinated...which is usually quite considerable in and of itself. Nature is, fortunately, not a sterile environment.

What you're showing, however, isn't a problem from what I can see, either. It's just immature and hasn't attained its adult color yet. That's normal. But it can be hard to tell with the tips cut off.

Some color variance is normal, particularly with seed that's not all that well-matched (cough-Scott's-cough). But it will get better as the grass ages. Some of us do object to the normal color variance in mismatched seed, but it's a personal preference. Let's put it this way--if the colors "Hooker's Green" and "Sap Green" mean something to you and seeing them close together is bothersome, then you're probably going to dislike the color variance in the lawn you just planted.

If not, then no, you won't even notice it.

Thank you guys for the feedback! I was almost ready to mix up the roundup once again. Next year, I will stick with the Scotts "awesome blend" from the home depot instead. I used that earlier in the season and the grass looks 100% better even shortly after germination. Nice and fine blades with color that matches.

This is what Scotts says is in the Costco "supreme" blend:

(42% Creeping Red Fescue, 34% perennial ryegrass, 24% kentucky blue grass).

Your suggestions make sense to me.

There's nothing wrong with that, per se. The creeping red fescue will do well in shadier spots, but tolerates sun reasonably well up to a point. PR is a good grass, but the cultivar you got probably wasn't the best. KBG, ditto.

Contrary to the name, "creeping" red fescue really doesn't even creep. Not appreciably. The clumps just get bigger exceptionally slowly under extraordinarily good care, nothing like KBG's ability to tiller and spread. I really wish they wouldn't try to use that as a selling point, ditto with "tillering" fescues. They usually don't to the customer's expectations.

But that's why they mix 'em. The fescue does well in shade. The PR does well in sun under poor conditions, and sprouts fast. The KBG does well in sun under good conditions, self-repairs, but sprouts and develops slowly.