[6] He painted en-plein-air and The Herald noted that "Harold Herbert has made peculiarly his the sharp, bright light which characterises our summer landscape, and his warm color has a host of admirers.

[10] The Australian Watercolour Institute established in Sydney 21 August 1923 by six mostly British-born artists eminent in their era; Benjamin Edwin Minns, Martin Stainforth, Joseph Arthur Bennett, Charles Ephraim Smith Tindall, Alfred James Daplyn and Albert Henry Fullwood following the model of the British Royal Watercolour Society, founded in 1804, and the Royal Institute of Painters in Water Colours, founded in 1831.

[11] They adopted the  name ‘Australian Watercolour Institute,’ at a meeting in September and invited Herbert with eight other notable artists to be foundation committee members; Arthur Streeton, John Eldershaw, Sydney Long, Matthew James MacNally, H. Septimus Power, John William Tristram and Blamire Young, each paying one guinea membership fee.

Their inaugural exhibition at Anthony Horderns’ Fine Art Gallery, 25 March to 15 April 1924, was opened by  the Governor of New South Wales, Admiral Sir Dudley de Chair.

In 1927 he was co-opted beside Arthur Streeton; WB McInnes, Charles Wheeler, Napier Waller, Paul Montford and Alice Bale, by the National Gallery of Victoria trustees' Special Committee George Swinburne, JT Collins, John Longstaff and Norman MacGeorge to examine and report, employing their judgement as artists, on a consignment of Felton Bequest purchases of classical European art, most of which were refused by the committee.

[15] Joan Kerr notes that his 28 August 1936 cover for the Club’s 170th "corroborree" for Lord Somers is typical of racist attitudes of the era; it depicts Aboriginal Dad, Mum with luggage, and son carrying the vice-regal hat, welcoming him with the caption “Boss Excellency, you come alonga us.” The 'Klub’ [sic] mia-mia is shown in the distance.

Strong colour contrasts or schemes approaching monotone; the opposition of full darks and lights or the closest of values do not tax the medium as he handles it.

From water-colour he draws all the nuances he may require, and his decisive judgment places them just where and in what strength they are most needed...though exploiting his surroundings for the benefit of his handling, he does so with grace and the appearance of inevitability.