Define white and colored input signal

1. What is meant by white input signal and colored input in signal processing or adaptive filtering?
2. How can be can applied adaptive LMS and NLMS algorithm in smart antenna beamforming?
3. if in a matlab coding

u=randn(1,5024);
C=0.8;
W=u;
u=filter(1,[1,-C],W);

what does it mean (work function) by 4th line i.e, u=filter(1,[1,-C],W); ? Please ans my questions. its very urgent