If you visit peglegsam's Channel at YouTube and enter "rainbow" into his search box
(the one in the scrollable list of videos, not the YouTube search box at the top)
you will turn up these 111 lovely clips from Pete Seeger's Rainbow Quest TV program.
Then you can use your browser's search function to find a video from this list.
(I've added some information that the browser search will miss -- e.g., Hedy West in #62.)

1. Beers Family - Dumbarton's Drums (part 1 of 2)
2. Beers Family - Dumbarton's Drums (part 2 of 2)
3. Beers Family - In My Garden Grew Plenty of Thyme
4. Beers Family - The Connaughtman's Rambles
5. Bessie Jones - I'm Gonna Lay Down my Life for my Lord, Yonder Come Day, The Devil's Been to my House
6. Bessie Jones - Johnny Brown
7. Bessie Jones & Pete Seeger - "12 Days of Christmas" & "Shalom Chaverim"
8. Bessie Jones & Pete Seeger - "We Wish You A Merry Christmas" & "Children, Go Where I Send Thee"
9. Buffy Sainte-Marie - Little Wheel Spin and Spin
10. Buffy Sainte-Marie - Men of the Fields
11. Buffy Sainte-Marie - My Country 'Tis of Thy People You're Dying
12. Buffy Sainte-Marie & Pete Seeger - Cindy
13. Buffy Sainte-Marie demonstrates the mouth bow
14. Clancy Brothers - I Never Will Play the Wild Rover No More
15. Cousin Emmy - Going Down the Road Feeling Bad
16. Cousin Emmy - Turkey in the Straw
17. Cousin Emmy - You Are My Sunshine
18. Cousin Emmy, Stanley Brothers and the Clinch Mountain Boys
19. Doc Watson - St. James Hospital (Streets of Laredo)
20. Doc Watson, Clint Howard, and Fred Price - Cackling Hen
21. Donovan, Shawn Phillips, Rev. Gary Davis, and Pete Seeger
22. Dr. Bernice Johnson Reagon - Steal Away to Jesus
23. Dr. Bernice Johnson Reagon - Titanic Blues
24. Dr. Bernice Johnson Reagon - Will the Circle Be Unbroken
25. Dr. Ralph Stanley - The Clinch Mountain Backstep
26. Elizabeth Cotten - Freight Train
27. Elizabeth Cotten - Mama, Your Papa Loves You
28. Elizabeth Cotten - Wilson Rag
29. Frank Warner & Pete Seeger - Tom Dooley (Frank Proffitt)
30. Grant Rogers - Bessie The Heifer
31. Grant Rogers - Tales of My Grandad
32. Grant Rogers - The Ballad of Pat McBraid
33. Grant Rogers - When a Fellow is Out of the Job
34. Grant Rogers & Pete Seeger
35. Hedy West - Ballad of William Moore
36. Herbert Levy - pennywhistle
37. Herbert Manana and Pete Seeger - Tina Sizwe (We Africans)
38. Jack Elliott, Pete Seeger, & Malvina Reynolds - Woody's Rag
39. Jean Ritchie - Shady Grove
40. Jean Ritchie - Skip to my Lou
41. Jean Ritchie & Pete Seeger - Jenny Jenkins
42. Jean Ritchie, Pete Seeger, B.J. Reagon - O Mary, Don't You Weep
43. Jim and Hazel Garland - Jew's Harp - Turkey in the Straw - Sugar in the Gourd
44. Jim Garland - I Don't Want Your Millions, Mister
45. K.L. Wong & the Hi-Landers Steel Band - Mary Ann
46. Kim Loy Wong & the Hi-Landers Steel Band, Herbert Levy, and Pete Seeger --When the Saints Go Marchin' In
47. Kim Loy Wong and the Hi-Landers Steel Band
48. Len Chandler - Beans in my Ears
49. Len Chandler - Takin' Me Away From You Train
50. Len Chandler & Pete Seeger - Move on Over (John Brown's Body)
51. Malvina Reynolds - No Hole in My Head
52. Malvina Reynolds - The Little Red Hen
53. Malvina Reynolds - The New Restaurant
54. Malvina Reynolds - Turn Around
55. Mamou Cajun Band
56. Mamou Cajun Band
57. Mimi & Richard Farina - House Un-American Blues Activity Dream
58. Mimi & Richard Farina - Joy 'Round My Brain
59. Mimi & Richard Farina performing "Dopico" and "Celebration For A Grey Day"
60. Mimi & Richard Farina performing Pack Up Your Sorrows and a small chat with Mimi
61. Mimi and Richard Farina - Bold Marauder
62. Mississippi John Hurt. Hedy West, Pete Seeger - Goodnight Irene
63. New Lost City Ramblers - Man of Constant Sorrow
64. New Lost City Ramblers - Soldier and the Lady
65. New York Downtown Community School students & Pete Seeger - Beans in my Ears
66. Patrick Sky & Pete Seeger - Girl I Once Did Own, Coyote My Little Brother, Guabi Guabi
67. Patrick Sky - Keep on Laughin' and Walkin'
68. Patrick Sky - Separation Blues
69. Patrick Sky sings a South African folk song
70. Patrick Sky, Pennywhistlers, and Pete Seeger - Rosin the Bow
71. Paul Draper - Dance Improvisation
72. Paul Draper & Pete Seeger - Ain't Gonna Let Nobody Turn Me Around
73. Pennywhistlers - Portland Town
74. Pennywhistlers - Sto Mi e Milo
75. Pennywhistlers - Майка Рада
76. Pete Seeger - Abiyoyo
77. Pete Seeger - All Mixed Up
78. Pete Seeger - Blue Mountain Lake
79. Pete Seeger - Guantanamera
80. Pete Seeger - Little Boxes
81. Pete Seeger - Lolly-Too-Dum
82. Pete Seeger - Seventy Miles
83. Pete Seeger shows how to play "Skip to my Lou" on the banjo
84. Pete Seeger, Doc Watson, Clint Howard, & Fred Price - Careless Love
85. Pete Seeger, Martha Schlamme, & Abraham Stockman - Peat Bog Soldiers
86. Pete Seeger, Pat Sky, and the Pennywhistlers - No Sir No
87. Pete Seeger, Pham Duy, Steve Addiss, and Bill Crofut - Oh My Darling Clementine
88. Pete Seeger, Theodore Bikel, Rashid Hussain - Last Night I Had the Strangest Dream (Ed McCurdy)
89. Pete Seeger, Theodore Bikel, Rashid Hussain - Peace (Old Testament)
90. Ralph Marino & Federico Picciano - Eh Volla Volla
91. Ralph Marino & Pete Seeger - The Butcher Boy
92. Ralph Marino sings a South Italian folk song
93. Ralph Marino, Frank Cernuto, and Federico Picciano
94. Ramblin' Jack Elliott - San Francisco Bay Blues
95. Ramblin' Jack Elliott - Talking Merchant Marine
96. Ramblin' Jack Elliott & Pete Seeger - Portland Town & Mule Skinner Blues
97. Rev. Gary Davis
98. Rosa Valentin & Rafael Martinez - Aguinaldo
99. Roscoe Holcomb - Little Gray Mule
100. Ruth Rubin & Pete Seeger - Tumbalalaika (Dumbala Laika)
101. Sonia Malkine - 1
102. Sonia Malkine - 2
103. Sonia Malkine & Pete Seeger
104. Sonny Terry & Brownie McGhee - Cindy & Rock Island Line
105. Sonny Terry & Brownie McGhee - Down by the Riverside & Fighting a Losing Battle
106. Sonny Terry & Brownie McGhee - Easy Rider
107. Sonny Terry & Brownie McGhee - Hootin' the Blues
108. Sonny Terry & Brownie McGhee - I Couldn't Believe My Eyes
109. Sonny Terry & Brownie McGhee - In the Evening
110. Sonny Terry & Brownie McGhee - Key to the Highway
111. Stanley Brothers and the Clinch Mountain Boys

—BK