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}. However since this appeared to be an easier puzzle I didn’t use that property; if I had my walkthrough would have been a bit shorter.
This is a Killer-X.
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.
1. R1C1 = 1 (hidden single on D\, also for N1 but I spotted it on the diagonal first), no 2 in R1C2 + R2C1 (NC)
1a. R2C5 = 1 (hidden single in C5), no 2 in R13C5 + R2C46 (NC)
1b. R3C9 = 1 (hidden single in R3), no 2 in R24C9 + R3C8 (NC)
1c. R4C8 = 1 (hidden single in C8), no 2 in R4C7 + R5C8 (NC)
1d. R5C3 = 1 (hidden single in R5), no 2 in R46C3 + R5C24 (NC)
1e. R9C2 = 1 (hidden single in C2), no 2 in R8C2 + R9C13 (NC)
1f. R6C4 = 1 (hidden single in C4), no 2 in R6C5 + R7C4 (NC)
1g. R7C6 = 1 (hidden single in C6), no 2 in R68C6 + R7C57 (NC)
1h. R8C7 = 1 (hidden single in C7), no 2 in R8C8 + R9C7 (NC)
2. R9C9 = 9 (hidden single on D\, also for N9 but I spotted it on the diagonal first), no 8 in R8C9 + R9C8 (NC)
2a. R8C5 = 9 (hidden single in R8), no 8 in R79C5 + R8C46 (NC)
2b. R7C1 = 9 (hidden single in R7), no 8 in R68C1 + R7C2 (NC)
2c. R6C2 = 9 (hidden single in C2), no 8 in R5C2 + R6C3 (NC)
2d. R5C7 = 9 (hidden single in R5), no 8 in R46C7 + R5C68 (NC)
2e. R4C6 = 9 (hidden single in R4), no 8 in R3C6 + R4C5 (NC)
2f. R3C4 = 9 (hidden single in R3), no 8 in R24C4 + R3C35 (NC)
2g. R2C3 = 9 (hidden single in R2), no 8 in R1C3 + R2C2 (NC)
2h. R1C8 = 9 (hidden single in R1), no 8 in R1C79 + R2C8 (NC)
Time for some clean-ups.
Blue marks
No 2 in R1C5 -> no 8 in R1C4
No 2 in R4C3 -> no 8 in R4C2
No 2 in R4C9 -> no 8 in R5C9
No 8 in R6C1 -> no 2 in R5C1
No 8 in R6C7 -> no 2 in R6C8
No 8 in R9C5 -> no 2 in R9C6
Green marks
No 1 in R1C7 -> no 8 in R2C7
No 1,2 in R2C1 -> no 7 in R2C2 -> no 3 in R1C2 (blue)
No 1 in R2C2 -> no 8 in R2C1 + R3C2
No 1,2 in R2C4 -> no 7 in R1C4 -> no 3 in R1C5 (blue)
No 1 in R2C8 -> no 8 in R3C8
No 1,2 in R3C5 -> no 7 in R3C6 -> no 3 in R2C6 (blue)
No 1,2 in R3C8 -> no 7 in R2C8 -> no 3 in R2C9 (blue)
No 1 in R4C2 -> no 8 in R4C1
No 1 in R4C5 -> no 8 in R5C5
No 1,2 in R5C2 -> no 7 in R4C2 -> no 3 in R4C3 (blue)
No 1 in R5C6 -> no 8 in R6C6
No 1,2 in R5C8 -> no 7 in R5C9 -> no 3 in R4C9 (blue)
No 1 in R5C9 -> no 8 in R6C9
No 1,2 in R6C6 -> no 7 in R5C6
No 1 in R7C2 -> no 8 in R7C3
No 1 in R7C3 -> no 8 in R8C3
No 1 in R7C89 -> no 8 in R7C89
No 1 in R8C1 -> no 8 in R9C1
No 1 in R8C4 -> no 8 in R9C4
No 1,2 in R9C1 -> no 7 in R8C1 -> no 3 in R8C2 (blue)
No 1,2 in R9C7 -> no 7 in R9C8 -> no 3 in R8C8 (blue)
No 1 in R9C8 -> no 8 in R9C7
Red marks
No 9 in R1C2 -> no 2 in R1C3
No 9 in R1C5 -> no 2 in R1C6
No 8,9 in R2C1 -> no 2,3 in R3C1
No 8,9 in R2C7 -> no 2,3 in R3C7
No 9 in R2C9 -> no 2 in R1C9
No 9 in R3C1 -> no 2 in R3C2 -> no 7 in R3C3 (green)
No 9 in R3C7 -> no 2 in R2C7 -> no 7 in R1C7 (green)
No 8,9 in R4C1 -> no 3 in R5C1 -> no 7 in R6C1 (blue)
No 8,9 in R4C4 -> no 3 in R5C4
No 9 in R5C1 -> no 2 in R4C1
No 9 in R5C4 -> no 2 in R4C4 + R5C5 -> no 7 in R4C5 (green)
No 8,9 in R5C8 -> no 3 in R6C8 -> no 7 in R6C7 (blue)
No 8,9 in R6C6 -> no 3 in R6C5
No 9 in R6C8 -> no 2 in R6C9
No 8,9 in R7C5 -> no 3 in R7C4 -> no 7 in R8C4 (blue)
No 9 in R7C7 -> no 2 in R7C8 -> no 7 in R7C9 (green)
No 8,9 in R7C8 -> no 3 in R7C7
No 9 in R8C2 -> no 2 in R7C2 + R8C3 -> no 7 in R7C3 (green)
No 8,9 in R8C3 -> no 3 in R9C3
No 8,9 in R8C6 -> no 3 in R9C6 -> no 7 in R9C5 (blue)
No 9 in R8C8 -> no 2 in R8C9
3a. 2 in N5 only in R4C5 + R5C6, no 3 in R5C5 (NC)
3b. 8 in N5 only in R5C4 + R6C5, no 7 in R5C5 (NC)
3c. R5C5 = {456} -> no 4,5,6 in R5C4 + R6C5 (red + NC)
3d. Naked pair {78} in R5C4 + R6C5, locked for N5, no 6 in R5C5 (NC)
3e. R5C5 = {456} -> no 4,5,6 in R4C5 + R5C6 (green + NC)
3f. Naked pair {23} in R4C5 + R5C6, locked for N5, no 4 in R5C4 (NC)
3g. R5C5 = 5, placed for both diagonals
3h. Naked pair {46} in R4C4 + R6C6, locked for D\
Clean-up: no 4,6 in R1C2 + R9C8 (blue)
3i. Naked pair {23} in R2C2 + R3C3, locked for N1, no 4 in R3C2 (NC)
3j. R1C2 = {78} -> no 7 in R1C3 (NC)
3k. Naked pair {78} in R7C7 + R8C8, locked for N9, no 6 in R7C8 (NC)
3l. 8 in N7 only in R8C2 + R9C3, no 7 in R8C3 (NC)
3m. R8C3 = {3456} -> no 4,5,6 in R8C2 + R9C3 (red + NC)
3n. Naked pair {78} in R8C2 + R9C3, locked for N7, no 6 in R8C3 (NC)
Clean-up: no 4,6 in R8C1 (blue)
3o. R9C3 = {78} -> no 7 in R9C4 (NC)
3p. 5 in N7 only in R7C2 + R8C3, no 4,6 in R7C3 (NC)
3q. Naked pair {23} in R7C3 + R8C2, locked for N7
3r. Naked pair {23} in R37C3, locked for C3
3s. Naked pair {78} in R18C2, locked for C2
3t. R8C3 = {45} -> no 4 in R8C4 (NC)
Clean-up: no 6 in R7C4 (blue)
3u. R3C2 = {56} -> no 4,5,6 in R3C1 (red + NC)
3v. Naked pair {78} in R1C2 + R3C1, locked for N1
3w. R3C1 = {78}, no 7 in R4C1 (NC)
3x. R35C1 = {78} (hidden pair in C1), no 6 in R4C1 (NC)
Clean-up: no 4,6 in R6C1 (blue)
3y. Naked pair {23} in R68C1, locked for C1
3z. R4C1 = {45} -> no 4,6 in R4C2 (green + NC)
Clean-up: no 4,6 in R4C3 (blue)
3aa. Naked pair {23} in R4C2 + R6C1, locked for N4
3ab. Naked pair {78} in R4C3 + R5C1, locked for N4
3ac. Naked pair {23} in R4C25, locked for R4
4a. 2 in N2 only in R1C45 = [28] (blue) or R23C6 = [82] (blue), 8 in R1C5 + R2C6, locked for N2, no 7 in R1C6 (NC)
4b. R1C6 = {3456} -> no 4,6 in R1C5 + R2C6 (red + NC)
Clean-up: no 4,6 in R1C4 + R3C6 (blue)
4c. Naked pair {23} in R1C4 + R3C6, locked for N2
4d. Naked pair {78} in R1C5 + R2C6, locked for N2, no 6 in R1C6 (NC)
4e. R1C6 = {45} -> no 4,5 in R1C7 (NC)
4f. R2C6 = {78} -> no 7 in R2C7 (NC)
4g. R2C7 = {3456} -> no 4,6 in R3C7 (red + NC)
4h. R3C7 = {78} -> no 7 in R3C8 + R4C7 (NC)
4i. Naked pair {78} in R3C7 and R8C2, locked for D/
4j. R2C9 + R3C7 = {78} (hidden pair in N3)
Clean-up: no 4,6 in R2C8 (blue)
4k. Naked pair {23} in R2C8 + R7C3, locked for D/
4l. R2C8 = {23} -> no 3 in R2C7 + R3C8 (NC)
4m. R1C7 + R2C8 = {23} (hidden pair in N3), no 4 in R2C7 (NC)
5a. R4C39 = {78} (hidden pair in R4)
Clean-up: no 4,6 in R5C9 (blue)
5b. Naked pair {78} in R24C9, locked for C9
5c. R6C9 = {3456} -> no 4,6 in R6C8 (red + NC)
Clean-up: no 4,6 in R6C7
5d. Naked pair {23} in R5C9 + R6C7, locked for N6
5e. Naked pair {78} in R4C9 + R6C8, locked for N6
5f. Naked pair {23} in R16C7, locked for C7
5g. Naked pair {23} in R29C8, locked for C8
5h. R7C8 = {45} -> no 4,5,6 in R7C9 (green + NC)
5i. Naked pair {23} in R7C9 + R9C8, locked for N9
5j. Naked pair {23} in R57C9, no 4 in R6C9 (NC)
5k. R57C4 = {78} (hidden pair in C4), no 7 in R7C5 (NC)
Clean-up: no 6 in R8C4 (blue)
5l. R9C36 = {78} (hidden pair in R9), no 7 in R8C6 (NC)
Clean-up: no 4,6 in R9C5 (blue)
5m. Naked pair {23} in R8C4 + R9C5, locked for N8, no 4 in R9C4 (NC)
5n. Naked pair {78} in R7C4 + R9C6, locked for N8
[Now some short forcing chains to place the remaining 5s.]
6a. R1C4 = 2 => R1C7 = 3, no 4 in R1C6 (NC)
or R1C4 = 3, R1C7 = 2, R2C8 = 3 => R2C9 = 7 (blue), no 6 in R1C9 (NC) => R1C9 = 4
-> R1C6 = 5
6b. R9C4 = 5 (hidden single in C4)
6c. R4C3 = 7 => R4C2 = 3 (blue), no 4 in R4C1
or R4C3 = 8, R5C1 = 7, no 6 in R5C2 (NC) => R5C2 = 4
-> R4C1 = 5
6d. R6C9 = 5 (hidden single in R6)
6e. R2C7 = 5 (hidden single in R2)
6f. R3C2 = 5 (hidden single in R3)
6g. R7C8 = 5 (hidden single in R7)
6h. R8C3 = 5 (hidden single in R8)
Then working through the options starting from one of the {23} cells and applying NC leads to two possible solutions.