RGB strip and ULN2003

Grumpy_Mike:

will be able to mix different levels of blue by using an analogWrite

Yes the intensity of the colour will change with the PWM value you feed it. By mixing different values you will get different colours.
For an example of this see the last half of the video in my project:-
Hexome

Take that last circuit. Remove all the black wires that go to ground.
Connect pins 1 to 7 together. Do this for all three chips.
Connect pins 16 to 10 together. Do this for all three chips.

Then wire pin 8 of all chips to ground. Do not connect pin 7 to anything.

Ok, so 1-7 are all connected to the Arduino PIN, the 8th goes to GND, 10-16 to the RGB-PIN, but what happens to PIN 9?