Well, I always found it best to paint bone in layers. I start with a layer of scorched brown and let it dry, I then do a layer of of Bleach Bone leaving the deep areas such as eye sockets the scorched brown, then when that dries I high light the edges and rims with skull white.
This is from the Gamesworkshop website article on painting Dark Angel's Deathwing army, so all credit goes to them.
1) For the bone-colored Deathwing armor, start out with an undercoat of Skull White Spray Paint. Then, basecoat the model with Graveyard Earth. Once the Graveyard Earth is dry, wash the model with some watered-down Brown Ink and make sure the wash gets in all the crevices.
2) Next, for the second basecoat, apply a 2:1 mix of Bleached Bone to Graveyard Earth. Leave the crevices unpainted so that the darker color shows through.
3) Now, edge the corners of the armor with straight Bleached Bone. Make sure you water down your paints to achieve a more subtle transition between basecoat and highlight.
4) For the final highlight, paint the very corners and edges with an even mix of Bleached Bone and Skull White. Before you paint the highlight, sometimes its helpful to see where the light is hitting the model and paint your highlights accordingly.
http://www.games-workshop.com/gws/content/article.jsp?catId=cat440176a&pageMode=multi&categoryId=900004§ion=&pIndex=3&aId=2600021&start=4 Automatically Appended Next Post: For Painting Red, which is a big part of playing Blood Angels, I suggest doing a base coat of Mechrite Red, then do a mix of 1:1 Blood Red:Mechrite Red and that will give you a very nice bright red, but for a darker gorey red, I suggest using the layer of Mechrite Red and then instead of a Blood Red: Mechrite Mix, do a Blood Red: Chaos Black Mix.