Are the aforementioned actions - such as counting the rak'ahs on one's fingers, focusing on specific colors in clothing, and raising one's voice slightly during some dhikr to ensure the performance of the pillars - considered valid in prayer to overcome a lack of concentration?

There is no harm in counting the rak'ahs of prayer with one's fingers for someone in this situation, even if it is not originally legislated. Focusing on the colors of clothing diminishes the devotion of prayer, and it is better to fill your prayer with devotion and presence of heart. What is happening is waswasa (whispering) and deception from Satan, because preoccupation with counting and focusing on colors wastes devotion, which is the spirit and essence of prayer. If the Prophet, peace and blessings be upon him, was distracted by an embroidered garment with markings, then what is happening now is even more distracting and contrary to the purpose of prayer.