you have those blue bolb? well they are painted bolb.... so they will have this problem... if you go HID you won't have problem as such... but it's big investment... and I dunno if it's legal at ur location.
If the outer clear plastic is yellowing out, then get some Meguiars Plastic-X and buff the lens a bit. Also avoid any blue bulbs and find some of those +50 bulbs. Osram, Narva, Hella, Phillips etc make them and pretty easy to find.
Just be careful with HID... it's not exactly good. Sticking a rebased HID bulb in a headlight unit (which all retro HID kits are) designed for halogen will just make the glare unbearable for oncoming traffic. If you want to do it right with HID, find a car with HID standard, open it up, then open up your RAV's headlights and fit that in.
If the headlight plastic is yellowing, it is caused by the UV rays of the sun. You can try some Meguiars Plastic-X but since it works only on the surface it will remove oxidation but not the yellowing.
If you put in aftermarket so-called "high performance" or "HID" bulbs (which are not true HID) the initial high intensity color of the bulbs changes as the coloring on the bulb fades.
Most major bulb manufacturers say to replace your bulbs every 2 years or 50,000 miles. That could just be to sell more bulbs, but the glass does cloud and turn darker over time.
Buy a pair of high quality, German made H4 clear bulbs. I highly recommend the Philips Vision Plus or the Osram Silverstars, for about $28 with free shipping from the UK. I am using the Philips Vision Plus, which are very bright and white enough in color. See untouched photos on my website. You can order these bulbs online from: