Everytime I shampoo my haircolor gets duller looking
Then you are using the wrong shampoo. Haircolor does fade over time. Try using shampoo and conditioner made for colored hair – ColorVive for example, or something made for your hair color that will brighten the color and freshen it, to keep it from fading. There are many shampoos that have a little color right in the shampoo that help keep it fresh looking; the Aussie hair care line has several, as do ARTec and Redken. They usually come in shades for dark hair (black/brown), red hair colors, golden blonde colors, champagne blonde colors, and ash blonde colors. Check them out at a store to see which might work for you.
Everytime I shampoo my hair feels dryer and more brittle
You can either a) stop shampooing everyday (try shampooing every other day instead) or b) use deep conditioner treatments with every shampoo. You have just bleached/stripped/and-or colored your hair. You can’t treat it like you used to-the days of jumping in the shower using Prell 2-in-1 are over. Condition every time you shampoo unless your hair gets too oily, in which case, alternate deep conditioning with a lighter, everyday conditioner.
I condition every time I shampoo and my hair is still dry and brittle
Then you need some mega treatments. A good two weeks of hot oil, mud packs, protein packs, deep conditioning and leave in conditioner like Infusium23 Leave-In Treatment will help it. Alternate them; one day do the mud, the next day the protein pack, the next hot oil. Do the deep cond. and leave in treatment everyday. For severe damage, see my section on damaged hair repair or call a salon for prof. advice.
My roots feel oily but my ends are splitting/dry.
You should always concentrate conditioner on the ends of hair. Apply 
conditioner from the middle of the shaft to the ends. The roots of your hair are closer to your scalp and are kept soft with the natural oils your scalp produces; they don’t really need additional conditioning. Any glosses or shine agents you apply should also only be applied to the dry or splitting ends of hair.