Mark has laid it all out beautifully, but I will make some additions.
"Colored" regiments are a continuation of the traditions of the shock troops of the Russian army during the period of the Provisional Government after the February Revolution. It was then that the "fashion" for colorful uniforms and various decorations on them appeared, which was intended to make service in shock troops more attractive, which were recruited exclusively from motivated volunteers and had the loud names of "shock", "revolutionary" or "death units" (as a symbol of readiness to die for the revolution). So such units really had high morale. After the Bolsheviks came to power, these shock units almost in full force took the path of fighting them. An interesting detail is that these units had different political preferences. For example, the Kornilov Regiment during the Provisional Government was called the "Slavic Shock Regiment" (there were many Czechoslovaks in its ranks) and had a social democratic orientation. The Markov and Drozdovsky Regiments had a monarchist orientation. The Alekseevsky Regiment adhered to a liberal political orientation. On this basis, friction often occurred between these units. For example, a case is described when, in response to the performance of the Tsar's anthem, the Kornilovites fired on the camp of their opponents (though without any consequences).
However, all this did not prevent them from effectively fighting together against the Bolsheviks and even in some ways was beneficial, causing competition in military exploits. By the way, at the first stage of the struggle, the Markovsky Regiment was called "Officer", since it really consisted to a large extent of former officers of the Russian army who served as privates.
Another interesting point - in such units, a captain could often command colonels, since only ranks earned in the anti-Bolshevik struggle were "counted" and not previous merits. Wearing a colored uniform (or even just a colored cap), among other things, signified the status of a recognized member of the regiment and this right had to be earned in battle. Officer units were formed simply because the number of former officers willing to fight the Bolsheviks far exceeded the number of volunteers from other social groups. As a result, it was decided not to mix these people with other contingents, but to form separate units from them. Due to the fact that the overwhelming majority of them were well trained and had experience of the First World War, they were simply terrifying opponents for the poorly organized Bolshevik units in the first stage of the war. Over time, motivated volunteers were replaced by unmotivated mobilized (including mobilized officers), the quality of all White units steadily declined. At the same time, the quality of the Bolshevik troops, on the contrary, grew during the war.
Since 1919, the White armies in the South of Russia began to use British uniforms and weapons in significant quantities. Moreover, colored and officer units received these uniforms on a priority basis.