Green’s Dictionary of Slang

lavender n.

1. something good, desirable.

[UK]W. Pett Ridge Minor Dialogues 264: It ain’t all lavender.
[UK]C. Rook Hooligan Nights 160: It ain’t all lavender goin’ on beat around the Walk.
[US]Ade Hand-made Fables 292: Life is not all Lavender to one who has to stay up every Night so as to postpone his Creep to a Cell overlooking Steam which escapes from a Laundry.
[UK](con. 1860s) P. Ackroyd Dan Leno and the Limehouse Golem 75: It’s not all lavender.

2. flattery.

[US]T. Haliburton Clockmaker II 95: Cant carries sway always now. A large party in the House, and a wappin’ large party out o’ the house, must be kept quiet, conciliated [...] and John Canter is made Lord Lavender.
[US]T. Haliburton Sam Slick in England II 160: You insensibly flattered my vanity, by assenting to my self-sufficiency, in supposing I was exempt from that universal frailty of human nature; you ‘threw the Lavender’ well.

SE in slang uses

In phrases

lay up in lavender (v.)

see separate entry.