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b) For purposes of this section, a person receives notice if the
owner of the property or someone with apparent authority to act for the
owner provides notice to the person by oral or written communication.(c) In this section:
(1) "Entry" has the meaning assigned by Section 30.05(b).
(2) "License holder" has the meaning assigned by Section 46.035(f).
(3) "Written communication" means:
(A) a card or other document on which is written language
identical to the following:

"Pursuant to Section 30.06, Penal Code
(trespass by holder of license to carry a concealed handgun), a person licensed under Subchapter H, Chapter 411, Government Code (concealed handgun law), may not enter this property with a concealed handgun";

or
(B) a sign posted on the property that:
(i) includes the language described by Paragraph (A) in both
English and Spanish;
(ii) appears in contrasting colors with block letters at least
one inch in height; and
(iii) is displayed in a conspicuous manner clearly visible to
the public.
(d) An offense under this section is a Class A misdemeanor.
(e) It is an exception to the application of this section that the property
on which the license holder carries a handgun is owned or leased
by a governmental entity and is not a premises or other place on which
the license holder is prohibited from carrying the handgun under
Section 46.03 or 46.035.

The way I read this, if the letters are not 1 inch in height, its not a valid sign. The law specifically identifies the size of lettering. It is not clear at all on what "contrasting colors" are. I would think that contrasting colors would be subject to local interpretation while the size lettering is easily resolved with a ruler. If not 1 inch they don't meet the requirement for a valid sign.

P-Pac, you don't say which town this bank is in.

The white letters on glass type sign is pretty common. As to whether its legal or not may take a court case to determine as there is no definition of what constitutes contrasting colors.