If are terminating a 25-pair Amphenol Connector (RJ21X) on a M-66 punch down block, you have to understand the full NEMA (National Electrical Manufacturers Association) color-coding scheme.

This design uses paired colors (primary and secondary) to identify a pair of conductors. One conductor is the primary color with a stripe of the secondary color and the other conductor of the pair is the secondary color with a stripe of the primary.

For a 25-pair color, the full table of colors is:

Primary Secondary

---

White Blue
Red Orange
Black Green
Yellow Brown
Purple/Violet Slate

You can buy a m-66 Punch Down block with a 50-Pin Amphenol Conector to elminate
the need to punch down the Channel Bank side,
and just punch down the FXS Station sets and CO/FXO Lines

T1 50-Pin Amphenol Connector Pinouts -> 66 Punch Down Block
Card    Amp50  T/R          Primary/Secondary  66 'M' PunchDown Block Side 'A'
Channel PIN Signal WirePair Color              RowNumber
1       1   RING   1        Blue/White         1    
1       26  TIP    1        White/Blue         2
2       2   RING   2        Orange/White       3
2       27  TIP    2        White/Orange       4
3       3   RING   3        Green/White        5 
3       28  TIP    3        White/Green        6 
4       4   RING   4        Brown/White        7
4       29  TIP    4        White/Brown        8
5       5   RING   5        Slate/White        9 
5       30  TIP    5        White/Slate       10
6       6   RING   6        Blue/Red          11
6       31  TIP    6        Red/Blue          12
7       7   RING   7        Orange/Red        13
7       32  TIP    7        Red/Orange        14
8       8   RING   8        Green/Red         15
8       33  TIP    8        Red/Green         16 
9       9   RING   9        Brown/Red         17
9       34  TIP    9        Red/Brown         18  
10      10  RING  10        Slate/Red         19
10      35  TIP   10        Red/Slate         20
11      11  RING  11        Blue/Black        21
11      36  TIP   11        Black/Blue        22
12      12  RING  12        Orange/Black      23
12      37  TIP   12        Black/Orange      24
13      13  RING  13        Green/Black       25
13      38  TIP   13        Black/Green       26
14      14  RING  14        Brown/Black       27 
14      39  TIP   14        Black/Brown       28 
15      15  RING  15        Slate/Black       29 
15      40  TIP   15        Black/Slate       30
16      16  RING  16        Blue/Yellow       31
16      41  TIP   16        Yellow/Blue       32
17      17  RING  17        Orange/Yellow     33
17      42  TIP   17        Yellow/Orange     34
18      18  RING  18        Green/Yellow      35
18      43  TIP   18        Yellow/Green      36
19      19  RING  19        Brown/Yellow      37
19      44  TIP   19        Yellow/Brown      38
20      20  RING  20        Slate/Yellow      39
20      45  TIP   20        Yellow/Slate      40
21      21  RING  21        Blue/Purple       41
21      46  TIP   21        Purple/Blue       42
22      22  RING  22        Orange/Purple     43
22      47  TIP   22        Purple/Orange     44
23      23  RING  23        Green/Purple      45
23      48  TIP   23        Purple/Green      46
24      24  RING  24        Brown/Purple      47
24      49  TIP   24        Purple/Brown      48 
25      Not Used            Slate/Purple 
25 50   Not Used            Purple/Slate

DigiumT1 -> RJ-48(F) X-Over

Digium T1 Card                    Channel Bank RJ-48(F)
==============                    =================
Pin   Pair#   T/R   Color         Pin   T/R
---   -----   ---   -----         ---   ---
 1      2      T    white/orange   4     R1
 2      2      R    orange/white   5     T
 4      1      T    blue/white     1     R
 5      1      T    white/blue     2     T1
 3      Not assigned
 6      Not assigned
 7      Not assigned
 8      Not assigned

See also: crossover T1 cable