Cells adjacent to green marks must total less than 10, blue must total 10, red must total more than 10. Also NC so horizontally/vertically adjacent cells cannot be {12}, {23}, … {78}, {89}, so at least one of the cells adjacent to each green mark must contain one of 1,2,3 as they cannot be {45}; similarly at least one of the cells adjacent to each red mark must contain one of 7,8,9 as they cannot be {56}.
Prelims.
Delete 9 from cells either side of green marks.
Delete 5 from cells either side of blue marks.
Delete 1 from cells either side of red marks.
Clean-ups only as stated.
1a. 1 in N2 only in R3C45, locked for R3, no 2 in R3C45 (NC)
Clean-ups: no 1 in R2C45 -> no 8 in R23C45 (green)
No 8,9 in R2C4 -> no 2,3 in R1C4 (red)
No 8,9 in R2C5 -> no 2,3 in R1C5 + R2C6 (red)
1b. There are 7 red marks in N2, R12C4 must contain one of 7,8,9, R12C5 must contain one of 7,8,9 and R2C6 must contain one of 7,8,9 as otherwise cannot place for all the red marks -> R2C6 = {789}, no 7,8,9 in R1C6 + R3C456, no 8 in R2C7 (NC)
1c. R1C56 must contain one of 7,8,9 (red) -> R1C5 = {789}, no 8 in R1C4 (NC)
Clean-up: 8 in N2 only in R1C5 + R2C6 -> no 2 in R1C6 (red)
1d. R1C5 + R2C6 = {789}, R12C4 must contain one of 7,9 -> no 7 in R2C5
2. Exactly the same pattern of coloured marks is in N6, so the same steps except that one sideways NC doesn’t apply this time.
2a. 1 in N6 only in R6C78, locked for R6, no 2 in R6C78 (NC)
Clean-ups: no 1 in R5C78 -> no 8 in R56C78 (green)
No 8,9 in R5C7 -> no 2,3 in R4C7 (red)
No 8,9 in R5C8 -> no 2,3 in R4C8 + R5C9 (red)
2b. There are 7 red marks in N2, R45C7 must contain one of 7,8,9, R45C8 must contain one of 7,8,9, and R5C9 must contain one of 7,8,9 as otherwise cannot place for all the red marks -> R5C9 = {789}, no 7,8,9 in R4C9 + R6C789
2c. R4C89 must contain one of 7,8,9 (red) -> R4C8 = {789}, no 8 in R4C7 (NC)
Clean-up: 8 in N6 only in R4C8 + R5C9 -> no 2 in R4C9 (red)
2d. R4C8 + R5C9 = {789}, R45C7 must contain one of 7,9 -> no 7 in R5C8
2e. 1 in C4 only in R345C4, no 2 in R4C4 (NC)
3a. There are 7 green marks in N4, one of R4C23 and one of R56C1 must each contain one of 1,2,3, while R5C3 must contain one of 1,2,3 to satisfy the remaining green marks -> R5C3 = {123}, no 2,3 in R4C1 + R5C2 + R6C23, no 2 in R4C3 + R5C4 (NC)
Clean-up: no 7,8 in R4C2 (blue)
3b. There are 2 groups of red marks in N4, one of R45C1 must contain one of 7,8,9, while R6C2 must contain one of 7,8,9 to satisfy the remaining red marks -> R6C2 = {789}, no 8 in R57C2 + R6C13 (NC)
Clean-up: no 1,2,3 in R5C2 -> R4C2 = {123}, R5C1 = {23} (both green), then no 4,6 in R4C1 (blue)
3c. R4C2 + R5C3 must contain one 2,3 -> no 8 in R4C3 (green)
3d. R4C1 + R6C2 = {89} (hidden pair in N4), no 8,9 in R3C1, no 9 in R7C2 (NC)
Clean-up: no 3 in R4C2 (blue)
3e. Naked triple {123} in R4C2 + R5C13, locked for N4, 3 also locked for R5, no 4 in R5C2 (NC)
Clean-up: 3 in R5C13 -> no 7 in R5C2 (green)
3f. R4C2 = {12} -> no 2 in R3C2 (NC)
4. Exactly the same pattern of coloured marks is in N8, so the same steps apply except that one vertical NC doesn’t apply this time.
4a. There are 7 green marks in N8, one of R7C56 and one of R89C4 must each contain one of 1,2,3, while R8C6 must contain one of 1,2,3 to satisfy the remaining green marks -> R8C6 = {123}, no 2,3 in R7C4 + R8C5 + R9C56, no 2 in R7C6 + R8C7 (NC)
Clean-up: no 7,8 in R7C5 (blue)
4b. There are 2 groups of red marks in N8, one of R78C4 must contain one of 7,8,9, while R9C5 must contain one of 7,8,9 to satisfy the remaining red marks -> R9C5 = {789}, no 8 in R8C5 + R9C46 (NC)
4c. Clean-up: no 1,2,3 in R8C5 -> R7C5 = {123}, R8C4 = {23} (both green), then no 4,6 on R7C4 (blue)
4d. R7C5 + R8C6 must contain one of 2,3 -> no 8 in R7C6 (green)
4e. R7C4 + R8C9 = {89} (hidden pair in N8), no 8,9 in R6C4 + R7C3 (NC)
Clean-up: no 3 in R7C5 (blue)
4f. Naked triple {123} in R7C5 + R8C46, locked for N8, 3 also locked for R8, no 4 in R8C5 (NC)
Clean-up: 3 in R8C46 -> no 7 in R8C5 (green)
4g. R7C5 = {12} -> no 2 in R6C5 (NC)
4h. R8C4 = {23} -> no 2 in R8C3 (NC)
[I ought to have seen this sooner; I’ve moved this important step here to delete some later steps.]
5a. No 1,3 in R5C78 so must contain 2 (green), locked for R5 and N6
5b. R5C13 = [31], R4C2 = 2 -> R4C1 = 8 (blue), R6C2 = 9, R5C9 = 8 (hidden single in N6), no 7 in R3C1, no 3 in R3C2, no 4 in R6C1 (NC)
Clean-up: R5C1 = 3 -> no 7 in R6C1 (green)
5c. R4C8 = {79} -> no 8 in R3C8 (NC)
5d. 9 in N6 only in R4C78, locked for R4
5e. Naked pair {56} in R5C2 + R6C1, locked for N4, no 5,6 in R7C1 (NC)
5f. Naked pair {47} in R46C3, locked for C3
5g. 2 in R6 only in R6C46 -> no 3 in R6C5 (NC)
5h. 8 in R6 only in R6C56 -> no 7 in R6C56 (NC)
5i. R6C9 = {3456} -> no 4 in R6C8 (green+NC)
[It looks like it’s time to use a forcing chain.]
6a. Consider placements for R7C4 = {89}
R7C4 = 8, R7C5 = 2 (blue) => R8C4 = 3
or R7C4 = 9, R9C5 = 8, no 7 in R9C46 (NC) => R7C6 = 7 (hidden single in N8), no 3 in R8C6 (green) => R8C4 = 3 (hidden single in N8)
-> R8C4 = 3, no 4 in R9C4 (NC)
Clean-up: R8C4 = 3 -> no 7 in R9C4 (green)
6b. Naked pair {56} in R8C5 + R9C4, locked for N8, no 5,6 in R9C3 (NC)
6c. Naked pair {47} in R79C6, locked for C6
6d. R8C6 = {12} -> no 1 in R8C7 (NC)
6e. R2C6 = {89} -> no 9 in R2C7 (NC)
6f. R7C4 = 8 (hidden single in C4), R7C5 = 2 (blue), R8C6 = 1, R9C5 = 9, no 7 in R6C4 (NC)
Clean-up: no 1,2 in R2C5 -> no 7 in R2C4 (green)
No 1,2 in R4C6 -> no 7 in R4C5 (green)
6g. R1C5 = {78} -> no 7 in R1C4 (NC)
6h. R1C45 + R2C6 = [978] (hidden triple in N2), no 8 in R1C3, no 6 in R1C6 + R2C5, no 7 in R2C7 (NC)
Clean-up: R1C5 = 7 -> no 3 in R1C6 + R2C5 (red)
R2C6 = 8 -> no 2 in R3C6 (red)
6i. R1C6 + R2C5 = [54], no 4,6 in R1C7, no 3 in R3C5 (NC)
6j. Naked pair {16} in R3C45, 6 locked for R3 and N2 -> R2C4 = 2, R3C6 = 3, R456C6 = [692], R56C5 = [58], R56C4 = [74], R4C45 = [13], R46C3 = [47], R4C9 = 5, R5C2 + R6C1 = [65], R8C5 + R9C4 = [65], no 3 in R2C3, no 5 in R3C3, no 2,4 in R3C7, no 4 in R3C9, no 7 in R4C7, no 1,3 in R6C7, no 4 in R7C1, no 6 in R7C3 (NC)
6k. R4C78 = [97], R6C789 = [613], no 8 in R3C7, no 2 in R5C8, no 5,7 in R7C7, no 4 in R7C9 (NC)
6l. R5C78 = [24]
6m. R1C9 = 4 (hidden single in N3), no 3 in R1C8 (NC)
6n. R7C3 = {35} -> no 4 in R7C2 (NC)
6o. 8 in R3 only in R3C23, locked for N1, no 7 in R3C2, no 9 in R3C3 (NC)
6p. 7,9 in N1 only in R2C123, locked for R2
6q. R9C1 = 6 (hidden single in N7), no 7 in R8C1 + R9C2 (NC)
6r. R1C1 = {12} -> no 1 in R1C2 + R2C1 (NC)
6s. R1C2 = 3 -> no 2 in R1C13 (NC)
6t. R1C1378 = [1682], no 5 in R2C3, no 3 in R2C8 (NC)
6u. R2C123 = [759], R2C789 = [361], no 4 in R3C2, no 8 in R3C7, no 5 in R3C8 (NC)
6v. R3C789 = [597], R789C9 = [692], no 5 in R7C8, no 8 in R8C8, no 3 in R9C8 (NC)
6w. R789C8 = [358], no 4 in R7C7, no 4 in R8C7, no 7 in R9C7 (NC)
The rest is naked singles, without using NC or coloured marks.