Python, 358 281 268 221 bytes

from time import* import os A='%-99o'%int('t12q2lxqkap48euoej9429cstbnazg84zyxflqzi8k1',36) f=open('/dev/urandom') for i in'0123456': t=os.fork() while t<1:T=int(time())%50;(sleep,(id,f.readlines)[i<A[T+49]])[i<A[T]](1) 

Python, 358 281 268 221 194 bytes

import os,time A='%-99o'%int('t12q2lxqkap48euoej9429cstbnazl63ubyryteo49u',36) for i in'0123456': t=os.fork() while t<1:T=int(time.time())%50;(time.sleep,(id,os.urandom)[i<A[T+49]])[i<A[T]](1) 

Monochrome is so last year. This uses multiprocessing and syscalls to achieve two color CPU graphs!

from time import* import os A='%-99o'%int('t12q2lxqkap48euoej9429cqv3ek6cy28iluqbnfk5t',36) f=open('/dev/urandom') for i in'0123456': t=os.fork() while t<1:T=int(time())%50;(sleep,(id,f.readlines)[i<A[T+49]])[i<A[T]](1) 

This code assumes you have 8 cores. It should be pretty easy to modify for fewer/more. It is portable to Linux/UNIX systems, and should produce the same two-color output for any CPU monitor that can distinguish User from System CPU time.

Monochrome is so last year. This uses multiple processes and syscalls to achieve two color CPU graphs!

from time import* import os A='%-99o'%int('t12q2lxqkap48euoej9429cstbnazg84zyxflqzi8k1',36) f=open('/dev/urandom') for i in'0123456': t=os.fork() while t<1:T=int(time())%50;(sleep,(id,f.readlines)[i<A[T+49]])[i<A[T]](1) 

This code assumes you have 8 cores. It should be pretty easy to modify for fewer/more. It is portable to Linux/UNIX systems (though it has only been tested on OS X), and should produce the same two-color output for any CPU monitor that can distinguish User from System CPU time.

Essentially, this works by forking off seven processes, each of which will choose to spend 1 second sleeping, spinning in usermode, or spinning the kernel. Spinning in kernel mode is achieved by requesting large globs of data from /dev/urandom, which forces the driver backing /dev/urandom to spend a lot of "system" CPU cycles.

Python, 358 281 268 bytes

from time import* from multiprocessing import* A='%-99o'%int('t12q2lxqkap48euoej9429cstbnazg84zyxflqzi8k1',36) f=open('/dev/urandom') def F(n): while 1:T=int(time())%50;(sleep,(id,f.readlines)[n<A[T+49]])[n<A[T]](1) for i in'012345':Process(None,F,i,i).start() F('6') 

Both outputs were generated with an update speed of 1s. No significant background tasks were running, though this output quite easily beats out any single-threaded CPU task.

This code assumes you have 8 cores. It should be pretty easy to modify for fewer/more. It is portable to Linux/UNIX systems, and should produce the same two-color output for any CPU monitor that can distinguish User from System CPU time.

Python, 358 281 268 221 bytes

from time import* import os A='%-99o'%int('t12q2lxqkap48euoej9429cqv3ek6cy28iluqbnfk5t',36) f=open('/dev/urandom') for i in'0123456': t=os.fork() while t<1:T=int(time())%50;(sleep,(id,f.readlines)[i<A[T+49]])[i<A[T]](1) 

All outputs were generated with an update speed of 1s. No significant background tasks were running, though this output quite easily beats out any single-threaded CPU task.

This code assumes you have 8 cores. It should be pretty easy to modify for fewer/more. It is portable to Linux/UNIX systems, and should produce the same two-color output for any CPU monitor that can distinguish User from System CPU time.

EDITED [07/21]: Shortened significantly by using fork() instead of multiprocessing.Process (/dev/urandom only works on *NIX systems anyway so this doesn't reduce portability). Note however that the program now spawns background tasks; you may have to killall Python (or similar) to get rid of the CPU-eaters.