Toroid Materials

Material Code	Color Code	Temp Stability (ppm / °C)	Usage (Wideband)	Usage (Power)	Usage (RFI Suppression)
0	Blue/Clear	0	150 kHz - 3 MHz
1	Blue/Clear	280	150 kHz - 3 MHz
2	Red/Clear	95	250 kHz - 10 MHz
2B	Red/Clear	95	250 kHz - 10 MHz
6	Yellow/Clear	35	3 - 40 MHz
7	White/Clear	30	1 - 25 MHz
10	Black/Clear	150	15 - 100 MHz
17	Blue/Yellow	50	20 - 200 MHz
31	Black	5700	1 - 300 MHz	0.5 - 30 MHz	1 - 500 MHz
43	Shiny Black	12500	5 - 400 MHz	0.5 - 30 MHz	5 - 500 MHz
52	Dull Black	2000	10 - 500 MHz	0.1 - 5 MHz	Above 10 MHz
61	Dull Black	1000	20 - 500 MHz	0.2 - 10 MHz	Above 20 MHz
67	Dull Black	500	50 - 100 MHz	0.5 - 30 MHz	Above 50 MHz
73	Shiny Black	1600			Below 30 MHz
75	Shiny Black	6000	1 - 50 MHz	0.1 - 3 MHz	Above 1 MHz
77	Shiny Black	7000	Up to 100 kHz

Note: 43 and 61 seem to be the most common for Ham Radio use in the USA, especially in the FT140 and FT240 sizes.