(1) chrom - name of the chromosome or scaffold. Chromosome names can be given with or without the 'chr' prefix.
(2) chromStart - Start position of the feature in standard chromosomal coordinates (i.e. first base is 0).
(3) chromEnd - End position of the feature in standard chromosomal coordinates
The next six fields are optional. Note that columns cannot be empty (ie: lower-numbered fields must always be populated if higher-numbered ones are used).
(4) name - Label to be displayed under the feature.
(5) score - A score between 0 and 1000.
(6) strand - defined as + (forward), - (reverse), or . (not applicable).
(7) thickStart - field used by UCSC drawing code, typically same as chromStart.
(8) thickEnd - field used by UCSC drawing code, typically same as chromEnd.
(9) itemRgb - an RGB color value (e.g. 0,0,255).
Coloring elements is fairly straightforward. First define RGB values for each track feature in the itemRgb field (9th column) and ensure fields 1-8 have appropriate values. Then, upload your track as a custom track (see above link) to UCSC. Once uploaded, click on the track name (usually "User Track") and edit the configuration to include: itemRgb="On". Other configuration values can be changed as well:
name - unique name to identify this track in the custom tracks list.
description - label to be displayed above the track in Genome Browser.
priority - integer defining the order in which to display tracks, if multiple tracks are defined.
useScore - a value from 1 to 4, which determines how scored data will be displayed. Additional parameters may be needed.
itemRgb - if set to 'on' (case-insensitive), the individual RGB values defined in tracks will be used.
Here's an example configuration: