The main difference between Color Oops, Effasol and L’Oreal Color Remover is that Color Oops has a special ingredient known as hydrosulfite. Hydrosulfite rapidly reduces the dye molecule without the need for bleach, ammonia, or peroxide.
Effasol is a Foaming Color Remover that can be used with water or peroxide. It acts a lot like Bleach, so you have to be careful when using it.
L’Oreal Color Remover (Also known as Color Zap) is used with peroxide and also acts like bleach, so again, careful using it. No Color remover will restore hair to its original, natural color. It removes the tint revealing the underlying base from which the natural color has been removed in the hair coloring process. But Color Oops is the only product that doesn’t use bleach, ammonia, or peroxide and is the gentlest of each removers listed. But it also is the most intensive to complete. And although the others use bleach based products, they are less abrasive and damaging to your hair than full strength bleach. Color Oops is a long process of mixing, adding it to your hair (Which I recommend using a shower cap to keep your head warm) and then rigorous rinsing and washing over and over. What Color Oops does is opens the cuticles of your hair and shrinks the color molecules, then through vigorous rinsing you get removal of that color. If you don’t rinse enough, I’ve found that these molecules return to their previous form and can cause hair to become darker after a few days, so following the instructions exactly is very important. It also has a strong smell that some people might not like because it’s a Sulfite base. But the smell does go away after rinsing and washing.
Effasol and L’Oreal Color Removers are much simpler to use. It’s a two part mix that goes directly onto your hair for a total of up to 60 minutes. (Again, a shower cap is recommended). Then a simple rinse and deep condition. I have used all three products. I really like that Color Oops doesn’t damage my hair, but found it only lightened it to a medium to light brown where as when I’ve used L’Oreal Color Remover on my hair, I’ve achieved a light orange to pale lemon yellow result. I’ve used all three products to remove Black and Unnatural Hair Colors with 100% success.
When trying to remove Black Dye, I find it easier, and better for my hair to use a color remover first, then deep condition, wait for a day and use a very gentle 20 volume bleach to remove the rest of the orange and yellow. I remember the old days when Bleaching was the only option for removal of Black Dye and using 30 Volume Peroxide scared me. But no more now that they’ve made Color Removers so much easier for the public to buy and use.