Sorry, b., you're quite right: I was getting mixed up myself! If you're still puzzling over 1a/1d, think of the "colour" that's not really a colour, you'll see how 1a begins (in conjunction with your "te"), then it's easy. Can I help you with any other specific clue? I would go for the 9 coloured cells with the simple colour: it's clear, I think, why the setter has used it so often.
Another thing: a long solution that has no clashing cells (so is entered straightforwardly) is 25a: first remove the obviously redundant letter from the clue. As 4d is also entered completely unaltered & no letter has to be removed from the clue, you then have quite a useful L shape to continue.