The helmet comes with caps that close up the vent holes.
I like it for the following reasons:
I've worn the petzl ecrin roc for years. It's alright. A little heavy, but it's cool to wear because it floats on your head w/ a suspension system.
I switched to the Meteor III
which is light, has HUGE vent holes, but is a little warm because it's the (non ansi approved) foam kind with no suspension inside. It sits right on your head.
Meteor III 235 grams
Ecrin Roc 475 grams
Altios 330 grams
From the petzl site:
The ALTIOS' hybrid suspension system, composed of a mesh panel and expanded polystyrene liner, makes this helmet extremely lightweight and comfortable to wear. Thanks to this innovative design, the helmet "levitates" above the head for a near-weightless feeling. The space between the head and the liner allows for effective ventilation with the Climate Control System
No yellow, but they do have orange!