Nice pics Billy,Thanks for sharing. The one with brown streaks is probably leopard skin. I'm not sure that the other types with color are more likely to break but are definitely harder to shape with good Constancy. As the shock wave travels through the rock it will hit those bands of color and distorts, causing waves in the fracture.
Those points look vary common for most that are around this area. I have seen many that are almost identical to those. I occasionally see some with color however,I have seen a few that are totally white, and a fair amount that are a pale gray and buttery smooth. Most are black but I have come across silver sheen, gold sheen,snowflake and some mahogany.
Given that black is most abundantand also the most consistant to work is the probable reason for the frequency. I would suspect that the colored one around here are for special purposes.
The sizes and styles that you have are spanning a huge range of time as you know. The smaller more fine notched are more present age and a few that you have are certainly more in the 8-10,000 yr. range.
Many recent finds in this area are pushing the dates of habitation but to some of the oldest in the North America.