You can achieve this by writing to the framebuffer directly using
dd There's no standard procedure or tool, because the details of what you need to write depend on the framebuffer format in your platform; i.e. it's different for every model of device.
dd if=/dev/urandom of=/dev/graphics/fb0
will get you a random colour in every pixel of your framebuffer. (If the framebuffer isn't at
/dev/graphics/fb0 on your device, you'll need to change the command accordingly.) To get a solid colour of your choice or a pattern, you'll need to find out what the framebuffer format is and think about it a bit.
An alternative way to do it is to set up the framebuffer with another application (e.g. a normal Android app that displays a full-screen colour), and then save the framebuffer to a file. This post explains the details of how to do it. The post is written for desktop Linux machines, but it works exactly the same way in Android, which uses the Linux kernel.