I try to keep the colors similar but I don't worry about minor variations. Hey, these are hand painted! The Wynken, Blynken, and Nod print on the left above was my original print. I just painted the one on the right and it came out a bit darker. I'm not sure which one I like better.
This isn't the usual way to make a colored relief print. It's not hard to do, but it's not really in line with the printmaking concept. Printmaking is a way to make multiple images in an edition that look exactly the same. I started painting black and white linocuts with watercolor started because I love relief prints, but I want to make them for children's illustration which doesn't need multiples. You only need a digital image that can be reproduced with modern publishing techniques.
The more traditional way to have colors in a print is to carve a block for each color and print them one at a time on top of each other. Here's a picture of one of my older prints that was made this way with 5 different blocks.
My friend Sherrie York does amazing linocuts with a third technique called a Reduction Linocut. First you carve a little bit out of the block and print all of the pieces of paper for your edition. Then you carve out more and print it again with a different color. Some of what you print the second time will cover or mingle with your first color. And you can keep carving and printing as many times as you want. she has a page of information about the process on her website www.sherrieyork.com
You should browse through her blog Brush and Baren where you can see lots of photos that document how she makes a print including this one called No Time Like the Present.
One place to see lots of different styles and techniques of hand-made prints is McClain's Printmaking Supplies Gallery. And while you're there you can buy some linoleum blocks and start carving!