Colourable

From colour + -able.

Full definition of colourable

1603, John Florio, translating Michel de Montaigne, Essays, II.8:Doth the master make any bargaine, or dispatch that pleaseth not? it is immediately smothered and suppressed, soone after forging causes, and devising colourable excuses, to excuse the want of execution or answer.
1612, John Smith, Proceedings of the English Colonie in Virginia, Chapel Hill 1988 (Select Edition of his Writings), p. 178:they told him their comming was for some extraordinary tooles and shift of apparell; by this colourable excuse, they obtained 6. or 7. more to their confederacie ....
2003, Ofer Raban, Modern legal theory and judicial impartiality, p. 83:These three examples have what may be called a 'colourable' claim for a public justification: they do not appear to us as checkerboard statues because, looking at the distinctions they draw, we presume the required justification does exist.

1590, Edmund Spenser, The Faerie Queene, III.iii:Glauce, what needs this colourable word,
To cloke the cause, that hath it selfe bewrayd?

1811, Daniel Ellis, Farther inquiries into the changes induced on atmospheric air, by the germination of seeds, the vegetation of plants, and the respiration of animals Chapter , This matter, however, is not itself coloured, but is only capable of exhibiting colours, by the addition of other matters : and hence we have ventured to call it the colourable, rather than the colouring parts of the plant, by which we merely indicate its property of becoming coloured, but not its actual possession of colour.
1978, A. G. Thomason, Hamiltonian Cycles and Uniquely Edge Colorable Graphs, These results were discovered whilst investigating uniquely edge colourable graphs.
1992, STACS 92, 9th Annual Symposium on Theoretical Aspects of Computer Science, edited by A. Finkel and M. Jantzen, page 397:A circle graph with no cycle of length four is colourable with three colours.

The following is perhaps not durably archived:

2010, October 4, J Murali, Sci-Tech
Internet : Online document sharing: expanding frontiers, This service offers all the essential colouring tools _ a pen, a pencil, colouring palette etc _ and presents a variety of colourable pictures for helping the child simulate a real colouring experience.

The sense "that can be coloured" is more common in American than in British English.