jackelopeFrom your pictures this is what I think I can tell you.
Yellow Sabot:
Is an MMP HPH-3P-EZ sabot. The sabot is 'contract' sabot made for Barnes and it is made with yellow polymer formulation.
Follow this link to see the sabot
https://mmpsabots.com/store/black-3petal-ez50-pcs/The black sabot is most likely a MMP HPH-12 sabot,
not an HPH-24. The 12 is the thickest of the 3 HPH 50 cal. sabots that MMP makes.
https://mmpsabots.com/store/black-hph12-sabot50-pcs/MMP does make another black sabot that has shorter petals and is slightly thicker. This sabot is made from te standard polymer formulation and was initially designed for the Savage Smokelss rifles - als worked very well in the older White 504 rifles.
The Black sabot are MMP factory sabots and
probably not purchased in a bullet packet from different bullet manufacturers.

SABOT Make, Model, Caliber Color Length Base Dia. Speer 270 gr. Horn.240gr. Nosler 185gr.
GDSP 0.4295" JHP 0.429" JHP 0.4505"
Harvester 44/50 Green 0.894" 0.500" 0.5035" 0.504"
Harvester Crush Rib 44/50 Green 0.887" 0.499" 0.503" 0.504"
MMP 44/50 Green 0.868" 0.494" 0.505" 0.505"
Hornady # 6750 44/50 Green 0.755" 0.494" 0.507" 0.5065"
Harvester Long 45/50 Black 0.948" 0.4975" 0.5025"
Harvester Short 45/50 Black 0.854" 0.499" 0.5025"
Harvester Crush Rib 45/50 Black 0.888" 0.498" 0.5015"
MMP HPH-24 45/50 Black 0.966" 0.497" 0.503"
MMP HPH-12 45/50 Black 0.972" 0.498" 0.505"
MMP EZ-3P 45/50 Black 0.829" 0.496" 0.5015"
Hope some of this helps