Cells adjacent to green marks must total 8 or 9, blue must total 10, red must total 11 or 12, yellow total less than 8, black total more than 12.
Also NC so horizontally/vertically adjacent cells cannot be {12}, {23}, … {78}, {89}, therefore at least one of the cells adjacent to each green or yellow mark must contain one of 1,2,3 as green cannot be {45}; similarly at least one of the cells adjacent to each red or black mark must contain one of 7,8,9 as red cannot be {56}.
Prelims.
Delete 9 from cells either side of green marks.
Delete 7,8,9 from cells either side of yellow marks.
Delete 5 from cells either side of blue marks.
Delete 1 from cells either side of red marks.
Delete 1,2,3 from cells either side of black marks.
Also delete 4 from R1C1 (two black marks)
Also delete 2 from R3C3 (two red marks)
Also delete 8 from R4C4 (two green marks)
Delete 4 from cells next to green marks (NC)
Delete 6 from cells next to red marks (NC)
That one made also delete 6 from cells with two yellow marks unnecessary.
Clean-ups and NCs only as stated.
1a. R3C1 = 1 (hidden single in N1) -> R2C1 = {78} (green)
1b. R1C1 = 6 (hidden single in N1), no 7 in R1C2 + R2C1 (NC)
1c. R2C1 = 8 -> R2C2 = 2 (blue)
1d. R1C1 = 6 -> R1C2 = 9 (black) -> R1C3 (red), R2C3 = 5, R3C2 = 4, R3C3 = 7
Clean-ups: no 2,4 in R1C4, no 4,6 in R2C4, no 6,8 in R3C4 + R4C3, no 2 in R4C1, no 3,5 in R4C2 (NC)
2. R3C78 = [25] (yellow)
Clean-ups: no 1,3 in R24C7, no 4,6 in R24C8, no 3 in R3C6, 6 in R3C9, then no 9 in R2C9, no 8,9 in R4C9 (NC)
2a. 3,6 in R3 only in R3C456, locked for N2
2b. 3 in R2 only in R2C89 -> no 4 in R2C9 (NC)
2c. 2 in R1 only in R1C56 -> no 1 in R1C56 (NC)
3a. R45C4 must contain one digit less than 4 (green) -> R4C4 = {123}
3b. R4C45 can only contain one digit less than 4 (green) -> no 2,3 in R4C5
3c. No 9 in R5C4 -> no 4 in R5C5 (black)
3d. R45C5 = {57} (red, only possible combination), locked for C5 and N5, no 6 in R3C5 + R4C6 + R5C46 + R6C5 (NC)
3e. R5C45 = [85] (black + NC), R4C4 = 1 (green), R4C5 = 7
Clean-ups: no 8 in R3C5, no 2 in R4C3, no 9 in R5C3 + R6C4, no 4 in R5C6 + R6C5 (NC)
3f. Naked pair {39} in R3C45, locked for R3 and N2 -> R2C4 = 7, R3C69 = [68], no 8 in R1C4 (NC)
3g. R1C4 = 5
3h. R6C4 = 6 (hidden single in N5)
3i. 4 in N5 only in R46C6, locked for C6 -> R2C56 = [41], no 2 in R1C6, no 3 in R3C5 (NC)
3j. R1C56 = [28], R3C45 = [39], R6C5 = 3, no 7 in R1C7, no 2,4 in R6C6 (NC)
3k. R456C6 = [429], R4C3 = 9, R5C4 = 6, no 8 in R4C2, no 5 in R4C7, no 1,3 in R5C7, no 8 in R6C7 (NC)
3l. R4C2 = 6, R4C7 = 8, no 5 in R4C1, no 7 in R5C2, no 7,9 in R6C7 (NC)
3m. R4C189 = [325], R5C123 = [714], R5C7 = 6, R2C789 = [936], R5C89 = [93], no 4 in R1C8, no 7 in R1C9, no 7 in R6C7, no 4 in R6C9 (NC)
3n. R1C8 = 7 (hidden single in N3) -> R6C9 = 7 (hidden single in N6)
3o. Naked pair {14} in R16C7, locked for C7
4a. Naked pair {37} in R7C67, locked for R7 (blue had been used in the Prelims to delete 5)
4b. Naked pair {58} in R67C2, locked for C2
4c. Naked triple {357} in R8C267, locked for R8
4d. Naked triple {357} in R9C267, locked for R9
4e. 5 in N7 only in R7C12 -> no 4 in R7C1
4f. 4 in N7 only in R89C1, R89C2 = {37} -> combined cage R89C12 = [4793/9347] (NC) -> R67C1 = {25}
[Alternatively 4 in N7 only in R89C1 = {49} (cannot be {24} which would eliminate 3 from N7, NC), 9 locked for C1 -> R67C1 = {25}]
4g. 1 in N7 only in R789C3 -> no 2 in R8C3 (NC)
[Alternatively this can be done with the final blue mark, which I haven’t yet used.]
4h. 2 in N9 only in R789C9 -> no 1 in R8C9 (NC)
5. R789C6 = {357}, R789C7 = {357} with no 5 in R7C67
5a. Either R89C6 = {57}, no 6 in R89C5 (NC) => R7C5 = 6 (hidden single in N8)
or R89C7 = {57}, no 6 in R89C8 (NC) => R7C8 = 6 (hidden single in N9)
-> 6 in R7C58, locked for R7
5b. Taking that further R7C67 = [37] => R7C8 = {14} (NC) => R7C5 = 6
or R7C67 = [73] => R7C5 = 1, R7C8 = 6
-> no 8 in R7C58
5c. 8 in R7 only in R7C23, locked for N7
5d. R8C34 = [19/64] (blue), no 2
[Cracked, the rest is straightforward.]
5e. Naked pair {49} in R8C14, locked for R8 -> R8C9 = 2, no 1 in R79C9 + R8C8 (NC)
5f. Naked pair {49} in R79C9, 4 locked for C9 and N9 -> R1C79 = [41], R6C78 = [14]
5g. Naked pair {16} in R7C58, 1 locked for R7
5h. Naked triple {258} in R7C123, 2 locked for R7 and N7
5i. R9C4 = 2 (hidden single in N8), no 1 in R9C35 (NC)
5j. R9C3 = 6, no 7 in R9C2 (NC)
5k. R8C3 = 1 -> R8C4 = 9 (blue), no 2 in R7C3 (NC)
5l. R89C5 = [68], no 5,7 in R8C6 (NC)
The rest is naked singles, without using NC or coloured marks.