The drawings are nice, especially the large head of the animal. Try this on practice paper, same as you use for drawings. You can give a light base coat of any of these 3 colors ultramarine, black cherry, or dahle purple. After this light coat, burnish it then apply your regular color and it should start making it as dark as you wish it to be. For the lights in the drawing you can take a putty eraser and pick out your lights. Like I say, practice this application on scrap paper. A little practice at this and you will see the difference it makes. Let me know how you make out. Burnish each coat as you put it on, do the picking last...Good luck...Adam
As an afterthought take one point of the fur and instead of single lines do it in groups flowing the same way the fur goes.
I love your drawing, it impressed me, and i look forward to see it at the end, i mean the large head, both "speak" to me as if i could say something to them, seems like alive.
Wannabe if you want to get darks use the main colour with dioxine violet and it seems to reflect the colour whatever it is. Try out on a piece of scrap paper. Fur is usually made up of lots of colours usually more than two. If you want a black do not use black from a tube, mix red, blue and a touch of yellow. This seems to have more depth. I think he is adorable.
I think your dogs are great. A little adjustment to the eye as Sketchart said.
I like using colored pencils and had the same problem with getting more intense color. Layering is the answer and don't be afraid to really put on some pressure. The first gentleman who responded had good advice (sorry forgot your name). Layering and mixing will solve your problem. If you look at my page you will see two pictures of flowers done with colored pencil. One is done pale on purpose to show the paper. The wild roses are intense and I did it by layers. burnish, layer some more! It's fun....!